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Apache Commons BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * The Bean Introspection Utilities component of the Apache Commons
 * subproject offers low-level utility classes that assist in getting and setting
 * property values on Java classes that follow the naming design patterns outlined
 * in the JavaBeans Specification, as well as mechanisms for dynamically defining
 * and accessing bean properties.
 *
 * Table of Contents
 *
 * 
 * 1. Overview
 *     
 *     1.1 Background
 *     1.2 External Dependencies
 *     
 * 
 * 2. Standard JavaBeans
 *     
 *     2.1 Background
 *     2.2 Basic Property Access
 *     2.3 Nested Property Access
 *     2.4 Customizing Introspection
 *     2.5 Suppressing Properties
 *     
 * 
 * 3. Dynamic Beans (DynaBeans)
 *     
 *     3.1 Background
 *     3.2 BasicDynaBean and BasicDynaClass
 *     3.3 ResultSetDynaClass (Wraps ResultSet in DynaBeans)
 *     3.4 RowSetDynaClass (Disconnected ResultSet as DynaBeans)
 *     3.5 WrapDynaBean and WrapDynaClass
 *     3.6 Lazy DynaBeans
 *     
 * 
 * 4. Data Type Conversions
 *     
 *     4.1 Background
 *     4.2 BeanUtils and ConvertUtils
 *         Conversions
 *     4.3 Defining Your Own Converters
 *     4.4 Locale Aware Conversions
 *     
 * 
 * 5. Utility Objects And Static Utility Classes
 * 6. Collections
 *     
 *     6.1 Comparing Beans
 *     6.2 Operating On Collections Of Beans
 *     6.3 Querying Or Filtering Collections Of Beans
 *     6.4 Transforming Collections Of Beans
 *     
 * 7. Frequently Asked Questions
 *     
 *     Why Can't BeanUtils Find My Method?
 *     How Do I Set The BeanComparator Order To Be Ascending/Descending?
 *     
 * 
 *
 * 
 * 1. Overview
 *
 * 
 * 1.1 Background
 *
 * The JavaBeans name comes from a
 * Java API
 * for a component architecture for the Java language.  Writing Java classes that
 * conform to the JavaBeans design patterns makes it easier for Java developers
 * to understand the functionality provided by your class, as well as allowing
 * JavaBeans-aware tools to use Java's introspection capabilities to
 * learn about the properties and operations provided by your class, and present
 * them in a visually appealing manner in development tools.
 *
 * The JavaBeans
 * Specification describes the complete set of characteristics that makes
 * an arbitrary Java class a JavaBean or not -- and you should consider reading
 * this document to be an important part of developing your Java programming
 * skills.  However, the required characteristics of JavaBeans that are
 * important for most development scenarios are listed here:
 * 
 * The class must be public, and provide a
 *     public constructor that accepts no arguments.  This allows
 *     tools and applications to dynamically create new instances of your bean,
 *     without necessarily knowing what Java class name will be used ahead of
 *     time, like this:
 *  *         String className = ...;
 *         Class beanClass = Class.forName(className);
 *         Object beanInstance = beanClass.newInstance();
 * 
 * As a necessary consequence of having a no-arguments constructor,
 *     configuration of your bean's behavior must be accomplished separately
 *     from its instantiation.  This is typically done by defining a set of
 *     properties of your bean, which can be used to modify its behavior
 *     or the data that the bean represents.  The normal convention for
 *     property names is that they start with a lower case letter, and be
 *     comprised only of characters that are legal in a Java identifier.
 * Typically, each bean property will have a public getter and
 *     setter method that are used to retrieve or define the property's
 *     value, respectively.  The JavaBeans Specification defines a design
 *     pattern for these names, using {@code get or set} as the
 *     prefix for the property name with it's first character capitalized.  Thus,
 *     you a JavaBean representing an employee might have
 *     (among others) properties named {@code firstName},
 *     {@code lastName, and hireDate}, with method signatures
 *     like this:
 *  *         public class Employee {
 *             public Employee();   // Zero-arguments constructor
 *             public String getFirstName();
 *             public void setFirstName(String firstName);
 *             public String getLastName();
 *             public void setLastName(String lastName);
 *             public Date getHireDate();
 *             public void setHireDate(Date hireDate);
 *             public boolean isManager();
 *             public void setManager(boolean manager);
 *             public String getFullName();
 *         }
 * 

 * As you can see from the above example, there is a special variant allowed
 *     for boolean properties -- you can name the getter method with a
 *     {@code is prefix instead of a get} prefix if that makes
 *     for a more understandable method name.

 * If you have both a getter and a setter method for a
 *     property, the data type returned by the getter must match the
 *     data type accepted by the setter.  In addition, it is contrary
 *     to the JavaBeans specification to have more than one setter
 *     with the same name, but different property types.
 * It is not required that you provide a getter and a
 *     setter for every property.  In the example above, the
 *     {@code fullName} property is read-only, because there is no
 *     setter method.  It is also possible, but less common, to provide
 *     write-only properties.
 * It is also possible to create a JavaBean where the getter and
 *     setter methods do not match the naming pattern described above.
 *     The standard JavaBeans support classes in the Java language, as well as
 *     all classes in the BeanUtils package, allow you to describe the actual
 *     property method names in a {@code BeanInfo} class associated with
 *     your bean class.  See the JavaBeans Specification for full details.
 * The JavaBeans Specification also describes many additional design patterns
 *     for event listeners, wiring JavaBeans together into component hierarchies,
 *     and other useful features that are beyond the scope of the BeanUtils
 *     package.
 * 

 *
 * Using standard Java coding techniques, it is very easy to deal with
 * JavaBeans if you know ahead of time which bean classes you will be using, and
 * which properties you are interested in:
 *  *         Employee employee = ...;
 *         System.out.println("Hello " + employee.getFirstName() + "!");
 * 
 *
 * 
 * 1.2 External Dependencies
 *
 * The commons-beanutils package requires that the following
 * additional packages be available in the application's class path at runtime:
 * 
 * 
 * 
 * Logging Package (Apache Commons), version 1.0 or later
 * 
 * Collections Package (Apache Commons), version 1.0 or later
 * 
 *
 * 
 * 2. Standard JavaBeans
 *
 * 
 * 2.1 Background
 *
 * As described above, the standard facilities of the Java programming language
 * make it easy and natural to access the property values of your beans using
 * calls to the appropriate getter methods.
 * But what happens in more sophisticated environments where you do not
 * necessarily know ahead of time which bean class you are going to be using,
 * or which property you want to retrieve or modify?  The Java language provides
 * classes like {@code java.beans.Introspector}, which can examine a Java
 * class at runtime and identify for you the names of the property getter and
 * setter methods, plus the Reflection capabilities to dynamically call
 * such a method.  However, these APIs can be difficult to use, and expose the
 * application developer to many unnecessary details of the underlying structure
 * of Java classes.  The APIs in the BeanUtils package are intended to simplify
 * getting and setting bean properties dynamically, where the objects you are
 * accessing -- and the names of the properties you care about -- are determined
 * at runtime in your application, rather than as you are writing and compiling
 * your application's classes.
 *
 * This is the set of needs that are satisfied by the static methods of the
 * {@link org.apache.commons.beanutils2.PropertyUtils}
 * class, which are described further in this section.  First, however, some
 * further definitions will prove to be useful:
 *
 * The general set of possible property types supported by a JavaBean can be
 * broken into three categories -- some of which are supported by the standard
 * JavaBeans specification, and some of which are uniquely supported by the
 * BeanUtils package:
 * 
 * Simple - Simple, or scalar, properties have a single
 *     value that may be retrieved or modified.  The underlying property type
 *     might be a Java language primitive (such as {@code int}, a simple
 *     object (such as a {@code java.lang.String}), or a more complex
 *     object whose class is defined either by the Java language, by the
 *     application, or by a class library included with the application.
 * Indexed - An indexed property stores an ordered collection
 *     of objects (all of the same type) that can be individually accessed by an
 *     integer-valued, non-negative index (or subscript).  Alternatively, the
 *     entire set of values may be set or retrieved using an array.
 *     As an extension to the JavaBeans specification, the
 *     BeanUtils package considers any property whose underlying data
 *     type is {@code java.util.List} (or an implementation of List) to be
 *     indexed as well.
 * Mapped - As an extension to standard JavaBeans APIs,
 *     the BeanUtils package considers any property whose underlying
 *     value is a {@code java.util.Map} to be "mapped".  You can set and
 *     retrieve individual values via a String-valued key.
 * 
 *
 * A variety of API methods are provided in the
 * {@link org.apache.commons.beanutils2.PropertyUtils} class to get and set
 * property values of all of these types.
 * In the code fragments below, assume that there are two bean classes defined
 * with the following method signatures:
 *  *     public class Employee {
 *         public Address getAddress(String type);
 *         public void setAddress(String type, Address address);
 *         public Employee getSubordinate(int index);
 *         public void setSubordinate(int index, Employee subordinate);
 *         public String getFirstName();
 *         public void setFirstName(String firstName);
 *         public String getLastName();
 *         public void setLastName(String lastName);
 *     }
 * 
 *
 * 
 * 2.2 Basic Property Access
 *
 * Getting and setting simple property values is, well,
 * simple :-).  Check out the following API signatures in the Javadocs:
 *
 * 
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getSimpleProperty(Object, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setSimpleProperty(Object, String, Object)}
 * 
 *
 * Using these methods, you might dynamically manipulate the employee's name
 * in an application:
 *  *     Employee employee = ...;
 *     String firstName = (String)
 *       PropertyUtils.getSimpleProperty(employee, "firstName");
 *     String lastName = (String)
 *       PropertyUtils.getSimpleProperty(employee, "lastName");
 *     ... manipulate the values ...
 *     PropertyUtils.setSimpleProperty(employee, "firstName", firstName);
 *     PropertyUtils.setSimpleProperty(employee, "lastName", lastName);
 * 
 *
 * For indexed properties, you have two choices - you can
 * either build a subscript into the "property name" string, using square
 * brackets, or you can specify the subscript in a separate argument to the
 * method call:
 *
 * 
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getIndexedProperty(Object, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getIndexedProperty(Object, String, int)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setIndexedProperty(Object, String, Object)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setIndexedProperty(Object, String, int, Object)}
 * 
 *
 * Only integer constants are allowed when you add a subscript to the property
 * name.  If you need to calculate the index of the entry you wish to retrieve,
 * you can use String concatenation to assemble the property name expression.
 * For example, you might do either of the following:
 *  *     Employee employee = ...;
 *     int index = ...;
 *     String name = "subordinate[" + index + "]";
 *     Employee subordinate = (Employee)
 *       PropertyUtils.getIndexedProperty(employee, name);
 *
 *     Employee employee = ...;
 *     int index = ...;
 *     Employee subordinate = (Employee)
 *       PropertyUtils.getIndexedProperty(employee, "subordinate", index);
 * 
 *
 * In a similar manner, there are two possible method signatures for getting
 * and setting mapped properties.  The difference is that the
 * extra argument is surrounded by parentheses ("(" and ")") instead of square
 * brackets, and it is considered to be a String-value key used to get or set
 * the appropriate value from an underlying map.
 *
 * 
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getMappedProperty(Object, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getMappedProperty(Object, String, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setMappedProperty(Object, String, Object)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setMappedProperty(Object, String, String, Object)}
 * 
 *
 * You can, for example, set the employee's home address in either of these
 * two manners:
 *
 *  *     Employee employee = ...;
 *     Address address = ...;
 *     PropertyUtils.setMappedProperty(employee, "address(home)", address);
 *
 *     Employee employee = ...;
 *     Address address = ...;
 *     PropertyUtils.setMappedProperty(employee, "address", "home", address);
 * 
 *
 * 
 * 2.3 Nested Property Access
 *
 * In all of the examples above, we have assumed that you wished to retrieve
 * the value of a property of the bean being passed as the first argument to a
 * PropertyUtils method.  However, what if the property value you retrieve is
 * really a Java object, and you wish to retrieve a property of that
 * object instead?
 *
 * For example, assume we really wanted the {@code city} property of the
 * employee's home address.  Using standard Java programming techniques for direct
 * access to the bean properties, we might write:
 *
 *  *     String city = employee.getAddress("home").getCity();
 * 
 *
 * The equivalent mechanism using the PropertyUtils class is called
 * nested property access.  To use this approach, you concatenate
 * together the property names of the access path, using "." separators -- very
 * similar to the way you can perform nested property access in JavaScript.
 *
 * 
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getNestedProperty(Object, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setNestedProperty(Object, String, Object)}
 * 
 *
 * The PropertyUtils equivalent to the above Java expression would be:
 *
 *  *     String city = (String)
 *       PropertyUtils.getNestedProperty(employee, "address(home).city");
 * 
 *
 * Finally, for convenience, PropertyUtils provides method signatures that
 * accept any arbitrary combination of simple, indexed, and mapped property
 * access, using any arbitrary level of nesting:
 *
 * 
 *  {@link org.apache.commons.beanutils2.PropertyUtils#getProperty(Object, String)}
 *  {@link org.apache.commons.beanutils2.PropertyUtils#setProperty(Object, String, Object)}
 * 
 *
 * which you might use like this:
 *
 *  *     Employee employee = ...;
 *     String city = (String) PropertyUtils.getProperty(employee,
 *       "subordinate[3].address(home).city");
 * 
 *
 * 
 * 2.4 Customizing Introspection
 *
 * As was pointed out, BeanUtils relies on conventions defined by the
 * JavaBeans specification to determine the properties available for
 * a specific bean class. Thus all classes conforming to these conventions can
 * be used out of the box.
 *
 * Sometimes an application has to deal with classes using different
 * conventions. For instance, fluent APIs allowing method chaining are not
 * compliant to the JavaBeans specification because here set methods
 * have non-void return values. From version 1.9.0 onwards, BeanUtils supports
 * customization of its introspection mechanism. This allows an application
 * to extend or modify the default discovery of bean properties.
 *
 * The key to this extension mechanism is the {@link org.apache.commons.beanutils2.BeanIntrospector}
 * interface. The purpose of an object implementing this interface is to
 * process a specific target class and create corresponding
 * {@code PropertyDescriptor} objects for the properties it detects.
 * Per default, BeanUtils uses a {@link org.apache.commons.beanutils2.DefaultBeanIntrospector}
 * object which detects properties compatible with the JavaBeans
 * specification.
 *
 * In order to extend the property discovery mechanism, {@code PropertyUtils}
 * offers the {@link org.apache.commons.beanutils2.PropertyUtils#addBeanIntrospector(BeanIntrospector)}
 * method. Here a custom {@code BeanIntrospector} implementation can be
 * passed in. During introspection of a class, this custom introspector is
 * then called, and it can add the properties it has detected to the total
 * result. As an example of such a custom {@code BeanIntrospector}
 * implementation, BeanUtils ships with the {@link org.apache.commons.beanutils2.FluentPropertyBeanIntrospector}
 * class. This implementation can detect properties whose set methods have a
 * non-void return type - thus enabling support for typical properties in a
 * fluent API.
 *
 * 
 * 2.5 Suppressing Properties
 * The mechanism of customizing bean introspection described in the previous
 * section can also be used to suppress specific properties. There is a
 * specialized {@code BeanIntrospector} implementation that does exactly
 * this: {@link org.apache.commons.beanutils2.SuppressPropertiesBeanIntrospector}.
 * When creating an instance, a collection with the names of properties that
 * should not be accessible on beans has to be provided. These properties will
 * then be removed if they have been detected by other {@code BeanIntrospector}
 * instances during processing of a bean class.
 *
 * A good use case for suppressing properties is the special {@code class}
 * property which is per default available for all beans; it is generated from the
 * {@code getClass() method inherited from Object} which follows the
 * naming conventions for property get methods. Exposing this property in an
 * uncontrolled way can lead to a security vulnerability as it allows access to
 * the class loader. More information can be found at
 * 
 * https://issues.apache.org/jira/browse/BEANUTILS-463.

 *
 * Because the {@code class} property is undesired in many use cases
 * there is already an instance of {@code SuppressPropertiesBeanIntrospector}
 * which is configured to suppress this property. It can be obtained via the
 * {@code SUPPRESS_CLASS} constant of
 * {@code SuppressPropertiesBeanIntrospector}.
 *
 * 
 * 3. Dynamic Beans (DynaBeans)
 *
 * 
 * 3.1 Background
 *
 * The {@link org.apache.commons.beanutils2.PropertyUtils} class described in the
 * preceding section is designed to provide dynamic property access on existing
 * JavaBean classes, without modifying them in any way.  A different use case for
 * dynamic property access is when you wish to represent a dynamically calculated
 * set of property values as a JavaBean, but without having to actually
 * write a Java class to represent these properties.  Besides the effort savings
 * in not having to create and maintain a separate Java class, this ability also
 * means you can deal with situations where the set of properties you care about
 * is determined dynamically (think of representing the result set of an SQL
 * select as a set of JavaBeans ...).
 *
 * To support this use case, the BeanUtils package provides the
 * {@link org.apache.commons.beanutils2.DynaBean} interface, which must be implemented by a
 * bean class actually implementing the interface's methods, and the associated
 * {@link org.apache.commons.beanutils2.DynaClass} interface that defines the set of
 * properties supported by a particular group of DynaBeans, in much the same way
 * that {@code java.lang.Class} defines the set of properties supported by
 * all instances of a particular JavaBean class.
 *
 * For example, the {@code Employee} class used in the examples above
 * might be implemented as a DynaBean, rather than as a standard JavaBean.  You
 * can access its properties like this:
 *
 *  *     DynaBean employee = ...; // Details depend on which
 *                              // DynaBean implementation you use
 *     String firstName = (String) employee.get("firstName");
 *     Address homeAddress = (Address) employee.get("address", "home");
 *     Object subordinate = employee.get("subordinate", 2);
 * 
 *
 * One very important convenience feature should be noted:  the
 * PropertyUtils property getter and setter methods understand how to access
 * properties in DynaBeans.  Therefore, if the bean you pass as the first
 * argument to, say, {@code PropertyUtils.getSimpleProperty()} is really a
 * DynaBean implementation, the call will get converted to the appropriate
 * DynaBean getter method transparently.  Thus, you can base your application's
 * dynamic property access totally on the PropertyUtils APIs, if you wish, and
 * use them to access either standard JavaBeans or DynaBeans without having to
 * care ahead of time how a particular bean is implemented.
 *
 * Because DynaBean and DynaClass are interfaces, they may be implemented
 * multiple times, in different ways, to address different usage scenarios.  The
 * following subsections describe the implementations that are provided as a part
 * of the standard BeanUtils package, although you are encouraged to
 * provide your own custom implementations for cases where the standard
 * implementations are not sufficient.
 *
 * 
 * 3.2 {@code BasicDynaBean and BasicDynaClass}

 *
 * The {@link org.apache.commons.beanutils2.BasicDynaBean} and
 * {@link org.apache.commons.beanutils2.BasicDynaClass} implementation provides a
 * basic set of
 * dynamic property capabilities where you want to dynamically define the
 * set of properties (described by instances of {@link org.apache.commons.beanutils2.DynaProperty}).
 * You start by defining the DynaClass that establishes
 * the set of properties you care about:
 *
 *  *     DynaProperty[] props = new DynaProperty[]{
 *         new DynaProperty("address", java.util.Map.class),
 *         new DynaProperty("subordinate", mypackage.Employee[].class),
 *         new DynaProperty("firstName", String.class),
 *         new DynaProperty("lastName",  String.class)
 *       };
 *     BasicDynaClass dynaClass = new BasicDynaClass("employee", null, props);
 * 
 *
 * Note that the 'dynaBeanClass' argument (in the constructor of
 * {@code BasicDynaClass) can have the value of null}.  In this
 * case, the value of {@code dynaClass.getDynaBeanClass} will just be the
 * {@code Class} for BasicDynaBean.

 *
 * Next, you use the {@code newInstance()} method of this DynaClass to
 * create new DynaBean instances that conform to this DynaClass, and populate
 * its initial property values (much as you would instantiate a new standard
 * JavaBean and then call its property setters):
 *
 *  *     DynaBean employee = dynaClass.newInstance();
 *     employee.set("address", new HashMap());
 *     employee.set("subordinate", new mypackage.Employee[0]);
 *     employee.set("firstName", "Fred");
 *     employee.set("lastName", "Flintstone");
 * 
 *
 * Note that the DynaBean class was declared to be
 * {@code DynaBean instead of BasicDynaBean}.  In
 * general, if you are using DynaBeans, you will not want to care about the
 * actual implementation class that is being used -- you only care about
 * declaring that it is a {@code DynaBean} so that you can use the
 * DynaBean APIs.

 *
 * As stated above, you can pass a DynaBean instance as the first argument
 * to a {@code PropertyUtils} method that gets and sets properties, and it
 * will be interpreted as you expect -- the dynamic properties of the DynaBean
 * will be retrieved or modified, instead of underlying properties on the
 * actual BasicDynaBean implementation class.
 *
 * 
 * 3.3 {@code ResultSetDynaClass} (Wraps ResultSet in DynaBeans)
 *
 * A very common use case for DynaBean APIs is to wrap other collections of
 * "stuff" that do not normally present themselves as JavaBeans.  One of the most
 * common collections that would be nice to wrap is the
 * {@code java.sql.ResultSet} that is returned when you ask a JDBC driver
 * to perform a SQL SELECT statement.  Commons BeanUtils offers a standard
 * mechanism for making each row of the result set visible as a DynaBean,
 * which you can utilize as shown in this example:
 *  *   Connection conn = ...;
 *   Statement stmt = conn.createStatement();
 *   ResultSet rs = stmt.executeQuery
 *     ("select account_id, name from customers");
 *   Iterator rows = (new ResultSetDynaClass(rs)).iterator();
 *   while (rows.hasNext()) {
 *     DynaBean row = (DynaBean) rows.next();
 *     System.out.println("Account number is " +
 *                        row.get("account_id") +
 *                        " and name is " + row.get("name"));
 *   }
 *   rs.close();
 *   stmt.close();
 * 
 *
 *
 * 
 * 3.4 {@code RowSetDynaClass} (Disconnected ResultSet as DynaBeans)
 * Although {@code ResultSetDynaClass} is
 * a very useful technique for representing the results of an SQL query as a
 * series of DynaBeans, an important problem is that the underlying
 * {@code ResultSet} must remain open throughout the period of time that the
 * rows are being processed by your application.  This hinders the ability to use
 * {@code ResultSetDynaClass} as a means of communicating information from
 * the model layer to the view layer in a model-view-controller architecture
 * such as that provided by the Struts
 * Framework, because there is no easy mechanism to assure that the result set
 * is finally closed (and the underlying {@code Connection} returned to its
 * connection pool, if you are using one).
 *
 * The {@code RowSetDynaClass} class represents a different approach to
 * this problem.  When you construct such an instance, the underlying data is
 * copied into a set of in-memory DynaBeans that represent the result.
 * The advantage of this technique, of course, is that you can immediately close
 * the ResultSet (and the corresponding Statement), normally before you even
 * process the actual data that was returned.  The disadvantage, of course, is
 * that you must pay the performance and memory costs of copying the result data,
 * and the result data must fit entirely into available heap memory.  For many
 * environments (particularly in web applications), this tradeoff is usually
 * quite beneficial.
 *
 * As an additional benefit, the {@code RowSetDynaClass} class is defined
 * to implement {@code java.io.Serializable}, so that it (and the
 * DynaBeans that correspond to each row of the result) can be conveniently
 * serialized and deserialized (as long as the underlying column values are
 * also Serializable).  Thus, {@code RowSetDynaClass} represents a very
 * convenient way to transmit the results of an SQL query to a remote Java-based
 * client application (such as an applet).
 *
 * The normal usage pattern for a {@code RowSetDynaClass} will look
 * something like this:
 *  *     Connection conn = ...;  // Acquire connection from pool
 *     Statement stmt = conn.createStatement();
 *     ResultSet rs = stmt.executeQuery("SELECT ...");
 *     RowSetDynaClass rsdc = new RowSetDynaClass(rs);
 *     rs.close();
 *     stmt.close();
 *     ...;                    // Return connection to pool
 *     List rows = rsdc.getRows();
 *     ...;                   // Process the rows as desired
 * 
 *
 *
 * 
 * 3.5 {@code WrapDynaBean and WrapDynaClass}

 *
 * OK, you've tried the DynaBeans APIs and they are cool -- very simple
 * {@code get() and set()} methods provide easy access to all
 * of the dynamically defined simple, indexed, and mapped properties of your
 * DynaBeans.  You'd like to use the DynaBean APIs to access all
 * of your beans, but you've got a bunch of existing standard JavaBeans classes
 * to deal with as well.  This is where the
 * {@link org.apache.commons.beanutils2.WrapDynaBean} (and its associated
 * {@link org.apache.commons.beanutils2.WrapDynaClass}) come into play.  As the name
 * implies, a WrapDynaBean is used to "wrap" the DynaBean APIs around an
 * existing standard JavaBean class.  To use it, simply create the wrapper
 * like this:

 *
 *  *     MyBean bean = ...;
 *     DynaBean wrapper = new WrapDynaBean(bean);
 *     String firstName = wrapper.get("firstName");
 * 
 *
 * Note that, although appropriate {@code WrapDynaClass} instances are
 * created internally, you never need to deal with them.
 *
 * 
 * 3.6 Lazy DynaBeans
 *
 * 
 *     1. LazyDynaBean - A Lazy
 *          {@link org.apache.commons.beanutils2.DynaBean}
 *     2. LazyDynaMap - A light weight
 *          {@link org.apache.commons.beanutils2.DynaBean} facade to a Map
 *          with lazy map/list processing
 *     3. LazyDynaList - A lazy list
 *          for {@link org.apache.commons.beanutils2.DynaBean DynaBean's},
 *          {@code java.util.Map}'s or POJO beans.
 *     4. LazyDynaClass - A
 *          {@link org.apache.commons.beanutils2.MutableDynaClass} implementation.
 * 
 *
 * You bought into the DynaBeans because it saves coding all those POJO JavaBeans but
 *    you're here because lazy caught your eye and wondered whats that about?
 *    What makes these flavors of DynaBean lazy are the following features:
 *     
 *         Lazy property addition - lazy beans use a
 *              {@link org.apache.commons.beanutils2.DynaClass} which implements
 *              the {@link org.apache.commons.beanutils2.MutableDynaClass}
 *              interface. This provides the ability to add and remove a DynaClass's
 *              properties. Lazy beans use this feature to automatically add
 *              a property which doesn't exist to the DynaClass when
 *              the {@code set(name, value)} method is called.
 *          Lazy List/Array growth - If an indexed property is not large
 *              enough to accomodate the {@code index being set then the List} or
 *              {@code Array} is automatically grown so that it is.

 *          Lazy List/Array instantiation - if an indexed
 *              property doesn't exist then calling the {@link org.apache.commons.beanutils2.DynaBean DynaBean's}
 *              indexed property getter/setter methods (i.e. {@code get(name, index)} or
 *              {@code set(name, index, value)) results in either a new List}
 *              or {@code Array} being instantiated. If the indexed property has not been
 *              defined in the DynaClass then it is automatically added and a default {@code List}
 *              implementation instantiated.

 *         Lazy Map instantiation - if a mapped
 *              property doesn't exist then calling the {@link org.apache.commons.beanutils2.DynaBean DynaBean's}
 *              mapped property getter/setter methods (i.e. {@code get(name, key)} or
 *              {@code set(name, key, value)) results in a new Map}
 *              being instantiated. If the mapped property has not been defined in the DynaClass
 *              then it is automatically added and a default {@code Map} implementation
 *              instantiated.

 *         Lazy Bean instantiation - if a property is defined in
 *              the {@code DynaClass as a DynaBean} or regular bean and
 *              doesn't exist in the {@code DynaBean then LazyDynaBean} wiill
 *              try to instantiate the bean using a default empty constructor.

 *     

 *
 * 1. {@link org.apache.commons.beanutils2.LazyDynaBean} is the standard lazy bean
 *    implementation. By default it is associated with a {@link org.apache.commons.beanutils2.LazyDynaClass}
 *    which implements the {@link org.apache.commons.beanutils2.MutableDynaClass} interface - however
 *    it can be used with any {@code MutableDynaClass} implementation. The question is how do
 *    I use it? - well it can be as simple as creating a new bean and then calling the getters/setters...
 *
 *  *     DynaBean dynaBean = new LazyDynaBean();
 *
 *     dynaBean.set("foo", "bar");                   // simple
 *
 *     dynaBean.set("customer", "title", "Mr");      // mapped
 *     dynaBean.set("customer", "surname", "Smith"); // mapped
 *
 *     dynaBean.set("address", 0, addressLine1);     // indexed
 *     dynaBean.set("address", 1, addressLine2);     // indexed
 *     dynaBean.set("address", 2, addressLine3);     // indexed
 * 
 *
 * 2. {@link org.apache.commons.beanutils2.LazyDynaMap} is a light weight
 *    {@code DynaBean facade to a Map} with all the usual lazy features. Its
 *    light weight because it doesn't have an associated {@code DynaClass} containing all the properties.
 *    In fact it actually implements the {@code DynaClass interface itself (and MutableDynaClass})
 *    and derives all the DynaClass information from the actual contents of the {@code Map}. A
 *    {@code LazyDynaMap can be created around an existing Map} or can instantiate its own
 *    {@code Map. After any DynaBean processing has finished the Map} can be retrieved
 *    and the DynaBean facade discarded.

 *
 * If you need a new {@code Map} then to use....
 *
 *  *     DynaBean dynaBean = new LazyDynaMap();        // create DynaBean
 *
 *     dynaBean.set("foo", "bar");                   // simple
 *     dynaBean.set("customer", "title", "Mr");      // mapped
 *     dynaBean.set("address", 0, addressLine1);     // indexed
 *
 *     Map myMap = dynaBean.getMap()                 // retrieve the Map
 * 
 * or to use with an existing {@code Map} ....
 *
 *  *     Map myMap = ....                             // exisitng Map
 *     DynaBean dynaBean = new LazyDynaMap(myMap);  // wrap Map in DynaBean
 *     dynaBean.set("foo", "bar");                  // set properties
 * 
 *
 * 3. {@link org.apache.commons.beanutils2.LazyDynaList}
 *      is  lazy list for {@link org.apache.commons.beanutils2.DynaBean DynaBeans}
 *      {@code java.util.Map}'s or POJO beans. See the Javadoc
 *      for more details and example usage.
 *
 * 4. {@link org.apache.commons.beanutils2.LazyDynaClass}
 *      extends {@link org.apache.commons.beanutils2.BasicDynaClass} and implements
 *      the MutableDynaClass interface.
 *      It can be used with other {@code DynaBean} implementations, but it
 *      is the default {@code DynaClass used by LazyDynaBean}.
 *      When using the {@code LazyDynaBean} there may be no need to have
 *      anything to do with the {@code DynaClass}. However sometimes there
 *      is a requirement to set up the {@code DynaClass} first - perhaps to
 *      define the type of array for an indexed property, or if using the DynaBean
 *      in restricted mode (see note below) is required. Doing so is
 *      straight forward...

 *
 * Either create a {@code LazyDynaClass} first...
 *
 * 
 *     MutableDynaClass dynaClass = new LazyDynaClass();    // create DynaClass
 *
 *     dynaClass.add("amount", java.lang.Integer.class);    // add property
 *     dynaClass.add("orders", OrderBean[].class);          // add indexed property
 *     dynaClass.add("orders", java.util.TreeMap.class);    // add mapped property
 *
 *     DynaBean dynaBean = new LazyDynaBean(dynaClass);     // Create DynaBean with associated DynaClass
 * 
 *
 * or create a {@code LazyDynaBean and get the DynaClass}...
 *
 * 
 *     DynaBean dynaBean = new LazyDynaBean();              // Create LazyDynaBean
 *     MutableDynaClass dynaClass =
 *              (MutableDynaClass)dynaBean.getDynaClass();  // get DynaClass
 *
 *     dynaClass.add("amount", java.lang.Integer.class);    // add property
 *     dynaClass.add("myBeans", myPackage.MyBean[].class);  // add 'array' indexed property
 *     dynaClass.add("myMap", java.util.TreeMap.class);     // add mapped property
 * 

 *
 * NOTE: One feature of {@link org.apache.commons.beanutils2.MutableDynaClass} is that it
 *    has a Restricted property. When the DynaClass is restricted no properties can be added
 *    or removed from the {@code DynaClass. Neither the LazyDynaBean or LazyDynaMap}
 *    will add properties automatically if the {@code DynaClass} is restricted.

 *
 *
 * 
 * 4. Data Type Conversions
 *
 * 
 * 4.1 Background
 *
 * So far, we've only considered the cases where the data types of the
 * dynamically accessed properties are known, and where we can use Java casts
 * to perform type conversions.  What happens if you want to automatically
 * perform type conversions when casting is not possible?  The
 * BeanUtils package provides a variety of APIs and design patterns
 * for performing this task as well.
 *
 * 
 * 4.2 {@code BeanUtils and ConvertUtils} Conversions

 *
 * A very common use case (and the situation that caused the initial creation
 * of the BeanUtils package) was the desire to convert the set of request
 * parameters that were included in a
 * {@code javax.servlet.HttpServletRequest} received by a web application
 * into a set of corresponding property setter calls on an arbitrary JavaBean.
 * (This is one of the fundamental services provided by the
 * Struts Framework, which uses
 * BeanUtils internally to implement this functionality.)
 *
 * In an HTTP request, the set of included parameters is made available as a
 * series of String (or String array, if there is more than one value for the
 * same parameter name) instances, which need to be converted to the underlying
 * data type.  The {@link org.apache.commons.beanutils2.BeanUtils} class provides
 * property setter methods that accept String values, and automatically convert
 * them to appropriate property types for Java primitives (such as
 * {@code int or boolean}), and property getter methods that
 * perform the reverse conversion.  Finally, a {@code populate()} method
 * is provided that accepts a {@code java.util.Map} containing a set of
 * property values (keyed by property name), and calls all of the appropriate
 * setters whenever the underlying bean has a property with the same name as
 * one of the request parameters.  So, you can perform the all-in-one property
 * setting operation like this:

 *
 *  *     HttpServletRequest request = ...;
 *     MyBean bean = ...;
 *     HashMap map = new HashMap();
 *     Enumeration names = request.getParameterNames();
 *     while (names.hasMoreElements()) {
 *       String name = (String) names.nextElement();
 *       map.put(name, request.getParameterValues(name));
 *     }
 *     BeanUtils.populate(bean, map);
 * 
 *
 * The {@code BeanUtils} class relies on conversion methods defined in
 * the {@link org.apache.commons.beanutils2.ConvertUtils} class to perform the actual
 * conversions, and these methods are availablve for direct use as well.
 * WARNING - It is likely that the hard coded use of
 * {@code ConvertUtils} methods will be deprecated in the future, and
 * replaced with a mechanism that allows you to plug in your own implementations
 * of the {@link org.apache.commons.beanutils2.Converter} interface instead.  Therefore,
 * new code should not be written with reliance on ConvertUtils.
 *
 * 
 * 4.3 Defining Your Own Converters
 *
 * The {@code ConvertUtils} class supports the ability to define and
 * register your own String --> Object conversions for any given Java class.
 * Once registered, such converters will be used transparently by all of the
 * {@code BeanUtils methods (including populate()}).  To
 * create and register your own converter, follow these steps:

 * 
 * Write a class that implements the {@link org.apache.commons.beanutils2.Converter}
 *     interface.  The {@code convert()} method should accept the
 *     {@code java.lang.Class} object of your application class (i.e.
 *     the class that you want to convert to, and a String representing the
 *     incoming value to be converted.
 * At application startup time, register an instance of your converter class
 *     by calling the {@code ConvertUtils.register()} method.
 * 
 *
 * 
 * 4.4 Locale Aware Conversions
 * The standard classes in {@code org.apache.commons.beanutils2} are not
 * locale aware. This gives them a cleaner interface and makes then easier to use
 * in situations where the locale is not important.
 * Extended, locale-aware analogues can be found in
 * org.apache.commons.beanutils2.locale
 * . These are built along the same
 * lines as the basic classes but support localization.
 *
 *
 * 
 * 5. Utility Objects And Static Utility Classes
 * 
 * Background
 * 
 * So far, the examples have covered the static utility classes ({@code BeanUtils},
 * {@code ConvertUtils and PropertyUtils}). These are easy to use but are
 * somewhat inflexible. These all share the same registered converters and the same caches.
 * 

 * 
 * This functionality can also be accessed through utility objects (in fact, the static utility
 * class use worker instances of these classes). For each static utility class, there is a corresponding
 * class with the same functionality that can be instantiated:
 * 
 *
 * 
 * 
 * 
 * 
 * 
 * 
 * Utility Objects And Static Utility ClassesStatic Utility Class Utility Object
BeanUtils BeanUtilsBean
ConvertUtils ConvertUtilsBean
PropertyUtils PropertyUtilsBean
 *
 * 
 * Creating an instances allow gives guarenteed control of the caching and registration
 * to the code that creates it.
 * 
 *
 * 
 * 6. Collections
 * 
 * 6.1 Comparing Beans
 * 
 * {@code org.apache.commons.beanutils2.BeanComparator is a Comparator} implementation
 * that compares beans based on a shared property value.
 * 

 * 
 * 6.2 Operating On Collections Of Beans
 * 
 * The {@code Closure interface in commons-collections} encapsulates a block of code that
 * executes on an arbitrary input Object. {@code Commons-collections} contains code that allows
 * {@code Closures} to be applied to the contents of a Collection. For more details, see the
 * commons-collections
 * documentation.
 * 

 * 
 * {@code BeanPropertyValueChangeClosure is a Closure} that sets a specified property
 * to a particular value. A typical usage is to combine this with {@code commons-collections}
 * so that all the beans in a collection can have a particular property set to a particular value.
 * 

 * For example, set the activeEmployee property to TRUE for an entire collection:
 *  
 *     // create the closure
 *     BeanPropertyValueChangeClosure closure =
 *         new BeanPropertyValueChangeClosure( "activeEmployee", Boolean.TRUE );
 *
 *     // update the Collection
 *     CollectionUtils.forAllDo( peopleCollection, closure );
 *   
 *
 * 
 * 6.3 Querying Or Filtering Collections Of Beans
 * 
 * The {@code Predicate interface in commons-collections} encapsulates an evaluation
 * of an input Object that returns either true or false. {@code Commons-collections} contains code
 * that allows
 * {@code Predicates} to be applied to be used to filter collections. For more details, see the
 * commons-collections
 * documentation.
 * 

 * 
 * {@code BeanPropertyValueEqualsPredicate is a Predicate} that evaluates a
 * set property value against a given value. A typical usage is
 * (in combination with {@code commons-collections})
 * to filter collections on the basis of a property value.
 * 

 * For example, to filter a collection to find all beans where active employee is false use:
 * 
 *     BeanPropertyValueEqualsPredicate predicate =
 *         new BeanPropertyValueEqualsPredicate( "activeEmployee", Boolean.FALSE );
 *
 *     // filter the Collection
 *     CollectionUtils.filter( peopleCollection, predicate );
 * 
 *
 * 
 * 6.4 Transforming Collections Of Beans
 * 
 * The {@code Transformer interface in commons-collections} encapsulates the transformation
 * of an input Object into an output object. {@code Commons-collections} contains code
 * that allows
 * {@code Transformers} to be applied produce a collection of outputs from a collection of inputs.
 * For more details, see the
 * commons-collections
 * documentation.
 * 

 * 
 * {@code BeanToPropertyTransformer is a Transformer} implementation
 * that transforms a bean into it's property value.
 * 

 * 
 * For example, to find all cities that are contained in the address of each person property of each bean in
 * a collection:
 * 
 *     
 *     // create the transformer
 *     BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city" );
 *
 *     // transform the Collection
 *     Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer );
 *     
 *
 * 
 * 7. Frequently Asked Questions
 *
 * 
 * Why Can't BeanUtils Find My Method?
 * The BeanUtils package relies on introspection rather than
 * reflection. This means that it will find only
 * JavaBean
 * compliant properties.
 * There are some subtleties  of this specification that can catch out the unwary:
 * 
 * A property can have only one set and one get method. Overloading is not allowed.
 * The {@code java.beans.Introspector} searches widely for a custom BeanInfo
 * class. If your class has the same name as another with a custom BeanInfo
 * (typically a java API class) then the {@code Introspector} may use that instead of
 * creating via reflection based on your class. If this happens, the only solution is to
 * create your own BeanInfo.
 * 
 *
 * 
 * How Do I Set The BeanComparator Order To Be Ascending/Descending?
 * 
 * BeanComparator relies on an internal Comparator to perform the actual
 * comparisions. By default, a natural ordering comparator
 * is used which imposes a natural order. If you want to change the order,
 * then a custom Comparator should be created and passed into the
 * appropriate constructor.
 * 
 * 
 * For example:
 * 
 * 
 *     import org.apache.commons.collections4.comparators.ComparableComparator;
 *     import org.apache.commons.collections4.comparators.ReverseComparator;
 *     import org.apache.commons.beanutils2.BeanComparator;
 *     ...
 *     BeanComparator reversedNaturalOrderBeanComparator
 *         = new BeanComparator("propertyName", new ReverseComparator(new ComparableComparator()));
 *     Collections.sort(myList, reversedNaturalOrderBeanComparator);
 *     ...
 * 
 */
package org.apache.commons.beanutils2;
org.apache.commons.beanutils2.package-info Maven / Gradle / Ivy

Table of Contents

1. Overview

1.1 Background

1.2 External Dependencies

2. Standard JavaBeans

2.1 Background

2.2 Basic Property Access

2.3 Nested Property Access

2.4 Customizing Introspection

2.5 Suppressing Properties

3. Dynamic Beans (DynaBeans)

3.1 Background

`3.2 {@code BasicDynaBean` and `BasicDynaClass}`

3.3 {@code ResultSetDynaClass} (Wraps ResultSet in DynaBeans)

3.4 {@code RowSetDynaClass} (Disconnected ResultSet as DynaBeans)

`3.5 {@code WrapDynaBean` and `WrapDynaClass}`

3.6 Lazy DynaBeans

4. Data Type Conversions

4.1 Background

`4.2 {@code BeanUtils` and `ConvertUtils} Conversions`

4.3 Defining Your Own Converters

4.4 Locale Aware Conversions

5. Utility Objects And Static Utility Classes

Background

6. Collections

6.1 Comparing Beans

6.2 Operating On Collections Of Beans

6.3 Querying Or Filtering Collections Of Beans

6.4 Transforming Collections Of Beans

7. Frequently Asked Questions

Why Can't BeanUtils Find My Method?

How Do I Set The BeanComparator Order To Be Ascending/Descending?

Static Utility Class	Utility Object
BeanUtils	BeanUtilsBean
ConvertUtils	ConvertUtilsBean
PropertyUtils	PropertyUtilsBean