org.apache.commons.beanutils.FluentPropertyBeanIntrospector 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.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.util.Locale;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
*
* An implementation of the BeanIntrospector interface which can
* detect write methods for properties used in fluent API scenario.
*
*
* A fluent API allows setting multiple properties using a single
* statement by supporting so-called method chaining: Methods for
* setting a property value do not return void, but an object which can
* be called for setting another property. An example of such a fluent API could
* look as follows:
*
*
* public class FooBuilder {
* public FooBuilder setFooProperty1(String value) {
* ...
* return this;
* }
*
* public FooBuilder setFooProperty2(int value) {
* ...
* return this;
* }
* }
*
*
* Per default, PropertyUtils does not detect methods like this
* because, having a non-void return type, they violate the Java Beans
* specification.
*
*
* This class is more tolerant with regards to the return type of a set method.
* It basically iterates over all methods of a class and filters them for a
* configurable prefix (the default prefix is set). It then
* generates corresponding PropertyDescriptor objects for the
* methods found which use these methods as write methods.
*
*
* An instance of this class is intended to collaborate with a
* {@link DefaultBeanIntrospector} object. So best results are achieved by
* adding this instance as custom {@code BeanIntrospector} after the
* DefaultBeanIntrospector object. Then default introspection finds
* read-only properties because it does not detect the write methods with a
* non-void return type. {@code FluentPropertyBeanIntrospector}
* completes the descriptors for these properties by setting the correct write
* method.
*
*
* @version $Id$
* @since 1.9
*/
public class FluentPropertyBeanIntrospector implements BeanIntrospector {
/** The default prefix for write methods. */
public static final String DEFAULT_WRITE_METHOD_PREFIX = "set";
/** The logger. */
private final Log log = LogFactory.getLog(getClass());
/** The prefix of write methods to search for. */
private final String writeMethodPrefix;
/**
*
* Creates a new instance of FluentPropertyBeanIntrospector and
* initializes it with the prefix for write methods used by the classes to
* be inspected.
*
* @param writePrefix the prefix for write methods (must not be null)
* @throws IllegalArgumentException if the prefix is null
*/
public FluentPropertyBeanIntrospector(final String writePrefix) {
if (writePrefix == null) {
throw new IllegalArgumentException(
"Prefix for write methods must not be null!");
}
writeMethodPrefix = writePrefix;
}
/**
*
* Creates a new instance of FluentPropertyBeanIntrospector and
* sets the default prefix for write methods.
*/
public FluentPropertyBeanIntrospector() {
this(DEFAULT_WRITE_METHOD_PREFIX);
}
/**
* Returns the prefix for write methods this instance scans for.
*
* @return the prefix for write methods
*/
public String getWriteMethodPrefix() {
return writeMethodPrefix;
}
/**
* Performs introspection. This method scans the current class's methods for
* property write methods which have not been discovered by default
* introspection.
*
* @param icontext the introspection context
* @throws IntrospectionException if an error occurs
*/
public void introspect(final IntrospectionContext icontext)
throws IntrospectionException {
for (final Method m : icontext.getTargetClass().getMethods()) {
if (m.getName().startsWith(getWriteMethodPrefix())) {
final String propertyName = propertyName(m);
final PropertyDescriptor pd = icontext
.getPropertyDescriptor(propertyName);
try {
if (pd == null) {
icontext.addPropertyDescriptor(createFluentPropertyDescritor(
m, propertyName));
} else if (pd.getWriteMethod() == null) {
pd.setWriteMethod(m);
}
} catch (final IntrospectionException e) {
log.info("Error when creating PropertyDescriptor for " + m
+ "! Ignoring this property.");
log.debug("Exception is:", e);
}
}
}
}
/**
* Derives the name of a property from the given set method.
*
* @param m the method
* @return the corresponding property name
*/
private String propertyName(final Method m) {
final String methodName = m.getName().substring(
getWriteMethodPrefix().length());
return (methodName.length() > 1) ? Introspector.decapitalize(methodName) : methodName
.toLowerCase(Locale.ENGLISH);
}
/**
* Creates a property descriptor for a fluent API property.
*
* @param m the set method for the fluent API property
* @param propertyName the name of the corresponding property
* @return the descriptor
* @throws IntrospectionException if an error occurs
*/
private PropertyDescriptor createFluentPropertyDescritor(final Method m,
final String propertyName) throws IntrospectionException {
return new PropertyDescriptor(propertyName(m), null, m);
}
}