org.apache.commons.beanutils.MappedPropertyDescriptor Maven / Gradle / Ivy
/*
* 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.
*/
package org.apache.commons.beanutils;
import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
/**
* A MappedPropertyDescriptor describes one mapped property.
* Mapped properties are multivalued properties like indexed properties
* but that are accessed with a String key instead of an index.
* Such property values are typically stored in a Map collection.
* For this class to work properly, a mapped value must have
* getter and setter methods of the form
* getProperty(String key) and
*
setProperty(String key, Object value),
*
where Property must be replaced
* by the name of the property.
* @see java.beans.PropertyDescriptor
*
* @version $Id$
*/
public class MappedPropertyDescriptor extends PropertyDescriptor {
// ----------------------------------------------------- Instance Variables
/**
* The underlying data type of the property we are describing.
*/
private Reference> mappedPropertyTypeRef;
/**
* The reader method for this property (if any).
*/
private MappedMethodReference mappedReadMethodRef;
/**
* The writer method for this property (if any).
*/
private MappedMethodReference mappedWriteMethodRef;
/**
* The parameter types array for the reader method signature.
*/
private static final Class[] STRING_CLASS_PARAMETER = new Class[]{String.class};
// ----------------------------------------------------------- Constructors
/**
* Constructs a MappedPropertyDescriptor for a property that follows
* the standard Java convention by having getFoo and setFoo
* accessor methods, with the addition of a String parameter (the key).
* Thus if the argument name is "fred", it will
* assume that the writer method is "setFred" and the reader method
* is "getFred". Note that the property name should start with a lower
* case character, which will be capitalized in the method names.
*
* @param propertyName The programmatic name of the property.
* @param beanClass The Class object for the target bean. For
* example sun.beans.OurButton.class.
*
* @throws IntrospectionException if an exception occurs during
* introspection.
*/
public MappedPropertyDescriptor(final String propertyName, final Class beanClass)
throws IntrospectionException {
super(propertyName, null, null);
if (propertyName == null || propertyName.length() == 0) {
throw new IntrospectionException("bad property name: " +
propertyName + " on class: " + beanClass.getClass().getName());
}
setName(propertyName);
final String base = capitalizePropertyName(propertyName);
// Look for mapped read method and matching write method
Method mappedReadMethod = null;
Method mappedWriteMethod = null;
try {
try {
mappedReadMethod = getMethod(beanClass, "get" + base,
STRING_CLASS_PARAMETER);
} catch (final IntrospectionException e) {
mappedReadMethod = getMethod(beanClass, "is" + base,
STRING_CLASS_PARAMETER);
}
final Class[] params = { String.class, mappedReadMethod.getReturnType() };
mappedWriteMethod = getMethod(beanClass, "set" + base, params);
} catch (final IntrospectionException e) {
/* Swallow IntrospectionException
* TODO: Why?
*/
}
// If there's no read method, then look for just a write method
if (mappedReadMethod == null) {
mappedWriteMethod = getMethod(beanClass, "set" + base, 2);
}
if ((mappedReadMethod == null) && (mappedWriteMethod == null)) {
throw new IntrospectionException("Property '" + propertyName +
"' not found on " +
beanClass.getName());
}
mappedReadMethodRef = new MappedMethodReference(mappedReadMethod);
mappedWriteMethodRef = new MappedMethodReference(mappedWriteMethod);
findMappedPropertyType();
}
/**
* This constructor takes the name of a mapped property, and method
* names for reading and writing the property.
*
* @param propertyName The programmatic name of the property.
* @param beanClass The Class object for the target bean. For
* example sun.beans.OurButton.class.
* @param mappedGetterName The name of the method used for
* reading one of the property values. May be null if the
* property is write-only.
* @param mappedSetterName The name of the method used for writing
* one of the property values. May be null if the property is
* read-only.
*
* @throws IntrospectionException if an exception occurs during
* introspection.
*/
public MappedPropertyDescriptor(final String propertyName, final Class beanClass,
final String mappedGetterName, final String mappedSetterName)
throws IntrospectionException {
super(propertyName, null, null);
if (propertyName == null || propertyName.length() == 0) {
throw new IntrospectionException("bad property name: " +
propertyName);
}
setName(propertyName);
// search the mapped get and set methods
Method mappedReadMethod = null;
Method mappedWriteMethod = null;
mappedReadMethod =
getMethod(beanClass, mappedGetterName, STRING_CLASS_PARAMETER);
if (mappedReadMethod != null) {
final Class[] params = { String.class, mappedReadMethod.getReturnType() };
mappedWriteMethod =
getMethod(beanClass, mappedSetterName, params);
} else {
mappedWriteMethod =
getMethod(beanClass, mappedSetterName, 2);
}
mappedReadMethodRef = new MappedMethodReference(mappedReadMethod);
mappedWriteMethodRef = new MappedMethodReference(mappedWriteMethod);
findMappedPropertyType();
}
/**
* This constructor takes the name of a mapped property, and Method
* objects for reading and writing the property.
*
* @param propertyName The programmatic name of the property.
* @param mappedGetter The method used for reading one of
* the property values. May be be null if the property
* is write-only.
* @param mappedSetter The method used for writing one the
* property values. May be null if the property is read-only.
*
* @throws IntrospectionException if an exception occurs during
* introspection.
*/
public MappedPropertyDescriptor(final String propertyName,
final Method mappedGetter, final Method mappedSetter)
throws IntrospectionException {
super(propertyName, mappedGetter, mappedSetter);
if (propertyName == null || propertyName.length() == 0) {
throw new IntrospectionException("bad property name: " +
propertyName);
}
setName(propertyName);
mappedReadMethodRef = new MappedMethodReference(mappedGetter);
mappedWriteMethodRef = new MappedMethodReference(mappedSetter);
findMappedPropertyType();
}
// -------------------------------------------------------- Public Methods
/**
* Gets the Class object for the property values.
*
* @return The Java type info for the property values. Note that
* the "Class" object may describe a built-in Java type such as "int".
* The result may be "null" if this is a mapped property that
* does not support non-keyed access.
*
* This is the type that will be returned by the mappedReadMethod.
*/
public Class getMappedPropertyType() {
return mappedPropertyTypeRef.get();
}
/**
* Gets the method that should be used to read one of the property value.
*
* @return The method that should be used to read the property value.
* May return null if the property can't be read.
*/
public Method getMappedReadMethod() {
return mappedReadMethodRef.get();
}
/**
* Sets the method that should be used to read one of the property value.
*
* @param mappedGetter The mapped getter method.
* @throws IntrospectionException If an error occurs finding the
* mapped property
*/
public void setMappedReadMethod(final Method mappedGetter)
throws IntrospectionException {
mappedReadMethodRef = new MappedMethodReference(mappedGetter);
findMappedPropertyType();
}
/**
* Gets the method that should be used to write one of the property value.
*
* @return The method that should be used to write one of the property value.
* May return null if the property can't be written.
*/
public Method getMappedWriteMethod() {
return mappedWriteMethodRef.get();
}
/**
* Sets the method that should be used to write the property value.
*
* @param mappedSetter The mapped setter method.
* @throws IntrospectionException If an error occurs finding the
* mapped property
*/
public void setMappedWriteMethod(final Method mappedSetter)
throws IntrospectionException {
mappedWriteMethodRef = new MappedMethodReference(mappedSetter);
findMappedPropertyType();
}
// ------------------------------------------------------- Private Methods
/**
* Introspect our bean class to identify the corresponding getter
* and setter methods.
*/
private void findMappedPropertyType() throws IntrospectionException {
try {
final Method mappedReadMethod = getMappedReadMethod();
final Method mappedWriteMethod = getMappedWriteMethod();
Class mappedPropertyType = null;
if (mappedReadMethod != null) {
if (mappedReadMethod.getParameterTypes().length != 1) {
throw new IntrospectionException
("bad mapped read method arg count");
}
mappedPropertyType = mappedReadMethod.getReturnType();
if (mappedPropertyType == Void.TYPE) {
throw new IntrospectionException
("mapped read method " +
mappedReadMethod.getName() + " returns void");
}
}
if (mappedWriteMethod != null) {
final Class[] params = mappedWriteMethod.getParameterTypes();
if (params.length != 2) {
throw new IntrospectionException
("bad mapped write method arg count");
}
if (mappedPropertyType != null &&
mappedPropertyType != params[1]) {
throw new IntrospectionException
("type mismatch between mapped read and write methods");
}
mappedPropertyType = params[1];
}
mappedPropertyTypeRef = new SoftReference>(mappedPropertyType);
} catch (final IntrospectionException ex) {
throw ex;
}
}
/**
* Return a capitalized version of the specified property name.
*
* @param s The property name
*/
private static String capitalizePropertyName(final String s) {
if (s.length() == 0) {
return s;
}
final char[] chars = s.toCharArray();
chars[0] = Character.toUpperCase(chars[0]);
return new String(chars);
}
/**
* Find a method on a class with a specified number of parameters.
*/
private static Method internalGetMethod(final Class initial, final String methodName,
final int parameterCount) {
// For overridden methods we need to find the most derived version.
// So we start with the given class and walk up the superclass chain.
for (Class clazz = initial; clazz != null; clazz = clazz.getSuperclass()) {
final Method[] methods = clazz.getDeclaredMethods();
for (final Method method : methods) {
if (method == null) {
continue;
}
// skip static methods.
final int mods = method.getModifiers();
if (!Modifier.isPublic(mods) ||
Modifier.isStatic(mods)) {
continue;
}
if (method.getName().equals(methodName) &&
method.getParameterTypes().length == parameterCount) {
return method;
}
}
}
// Now check any inherited interfaces. This is necessary both when
// the argument class is itself an interface, and when the argument
// class is an abstract class.
final Class[] interfaces = initial.getInterfaces();
for (Class interface1 : interfaces) {
final Method method = internalGetMethod(interface1, methodName, parameterCount);
if (method != null) {
return method;
}
}
return null;
}
/**
* Find a method on a class with a specified number of parameters.
*/
private static Method getMethod(final Class clazz, final String methodName, final int parameterCount)
throws IntrospectionException {
if (methodName == null) {
return null;
}
final Method method = internalGetMethod(clazz, methodName, parameterCount);
if (method != null) {
return method;
}
// No Method found
throw new IntrospectionException("No method \"" + methodName +
"\" with " + parameterCount + " parameter(s)");
}
/**
* Find a method on a class with a specified parameter list.
*/
private static Method getMethod(final Class clazz, final String methodName, final Class[] parameterTypes)
throws IntrospectionException {
if (methodName == null) {
return null;
}
final Method method = MethodUtils.getMatchingAccessibleMethod(clazz, methodName, parameterTypes);
if (method != null) {
return method;
}
final int parameterCount = (parameterTypes == null) ? 0 : parameterTypes.length;
// No Method found
throw new IntrospectionException("No method \"" + methodName +
"\" with " + parameterCount + " parameter(s) of matching types.");
}
/**
* Holds a {@link Method} in a {@link SoftReference} so that it
* it doesn't prevent any ClassLoader being garbage collected, but
* tries to re-create the method if the method reference has been
* released.
*
* See http://issues.apache.org/jira/browse/BEANUTILS-291
*/
private static class MappedMethodReference {
private String className;
private String methodName;
private Reference methodRef;
private Reference> classRef;
private Reference> writeParamTypeRef0;
private Reference> writeParamTypeRef1;
private String[] writeParamClassNames;
MappedMethodReference(final Method m) {
if (m != null) {
className = m.getDeclaringClass().getName();
methodName = m.getName();
methodRef = new SoftReference(m);
classRef = new WeakReference>(m.getDeclaringClass());
final Class[] types = m.getParameterTypes();
if (types.length == 2) {
writeParamTypeRef0 = new WeakReference>(types[0]);
writeParamTypeRef1 = new WeakReference>(types[1]);
writeParamClassNames = new String[2];
writeParamClassNames[0] = types[0].getName();
writeParamClassNames[1] = types[1].getName();
}
}
}
private Method get() {
if (methodRef == null) {
return null;
}
Method m = methodRef.get();
if (m == null) {
Class clazz = classRef.get();
if (clazz == null) {
clazz = reLoadClass();
if (clazz != null) {
classRef = new WeakReference>(clazz);
}
}
if (clazz == null) {
throw new RuntimeException("Method " + methodName + " for " +
className + " could not be reconstructed - class reference has gone");
}
Class[] paramTypes = null;
if (writeParamClassNames != null) {
paramTypes = new Class[2];
paramTypes[0] = writeParamTypeRef0.get();
if (paramTypes[0] == null) {
paramTypes[0] = reLoadClass(writeParamClassNames[0]);
if (paramTypes[0] != null) {
writeParamTypeRef0 = new WeakReference>(paramTypes[0]);
}
}
paramTypes[1] = writeParamTypeRef1.get();
if (paramTypes[1] == null) {
paramTypes[1] = reLoadClass(writeParamClassNames[1]);
if (paramTypes[1] != null) {
writeParamTypeRef1 = new WeakReference>(paramTypes[1]);
}
}
} else {
paramTypes = STRING_CLASS_PARAMETER;
}
try {
m = clazz.getMethod(methodName, paramTypes);
// Un-comment following line for testing
// System.out.println("Recreated Method " + methodName + " for " + className);
} catch (final NoSuchMethodException e) {
throw new RuntimeException("Method " + methodName + " for " +
className + " could not be reconstructed - method not found");
}
methodRef = new SoftReference(m);
}
return m;
}
/**
* Try to re-load the class
*/
private Class reLoadClass() {
return reLoadClass(className);
}
/**
* Try to re-load the class
*/
private Class reLoadClass(final String name) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
// Try the context class loader
if (classLoader != null) {
try {
return classLoader.loadClass(name);
} catch (final ClassNotFoundException e) {
// ignore
}
}
// Try this class's class loader
classLoader = MappedPropertyDescriptor.class.getClassLoader();
try {
return classLoader.loadClass(name);
} catch (final ClassNotFoundException e) {
return null;
}
}
}
}