Commons Beanutils example source code file (MappedPropertyDescriptor.java)

This example Commons Beanutils source code file (MappedPropertyDescriptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Beanutils tags/keywords

bean, class, class, introspectionexception, introspectionexception, javabean, mappedmethodreference, mappedmethodreference, mappedpropertydescriptor, method, method, reference, reflection, softreference, string, string_class_parameter, weakreference

The Commons Beanutils MappedPropertyDescriptor.java source code

/*
 * 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
 * <p>getProperty(String key) and
 * <p>setProperty(String key, Object value),
 * <p>where Property must be replaced
 * by the name of the property.
 * @see java.beans.PropertyDescriptor
 *
 * @author Rey Francois
 * @author Gregor Rayman
 * @version $Revision: 806915 $ $Date: 2009-08-23 01:50:23 +0100 (Sun, 23 Aug 2009) $
 */


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.
     *
     * @exception IntrospectionException if an exception occurs during
     *              introspection.
     */
    public MappedPropertyDescriptor(String propertyName, 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);
        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 (IntrospectionException e) {
                mappedReadMethod = getMethod(beanClass, "is" + base,
                        STRING_CLASS_PARAMETER);
            }
            Class[] params = { String.class, mappedReadMethod.getReturnType() };
            mappedWriteMethod = getMethod(beanClass, "set" + base, params);
        } catch (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.
     *
     * @exception IntrospectionException if an exception occurs during
     *              introspection.
     */
    public MappedPropertyDescriptor(String propertyName, Class beanClass,
                                    String mappedGetterName, 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) {
            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.
     *
     * @exception IntrospectionException if an exception occurs during
     *              introspection.
     */
    public MappedPropertyDescriptor(String propertyName,
                                    Method mappedGetter, 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.
     * <p>
     * This is the type that will be returned by the mappedReadMethod.
     */
    public Class getMappedPropertyType() {
        return (Class)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(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(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 {
            Method mappedReadMethod  = getMappedReadMethod();
            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) {
                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 (IntrospectionException ex) {
            throw ex;
        }
    }


    /**
     * Return a capitalized version of the specified property name.
     *
     * @param s The property name
     */
    private static String capitalizePropertyName(String s) {
        if (s.length() == 0) {
            return s;
        }

        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(Class initial, String methodName,
                                            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()) {
            Method[] methods = clazz.getDeclaredMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];
                if (method == null) {
                    continue;
                }
                // skip static methods.
                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.
        Class[] interfaces = initial.getInterfaces();
        for (int i = 0; i < interfaces.length; i++) {
            Method method = internalGetMethod(interfaces[i], 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(Class clazz, String methodName, int parameterCount)
            throws IntrospectionException {
        if (methodName == null) {
            return null;
        }

        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(Class clazz, String methodName, Class[] parameterTypes) 
                                           throws IntrospectionException {
        if (methodName == null) {
            return null;
        }

        Method method = MethodUtils.getMatchingAccessibleMethod(clazz, methodName, parameterTypes);
        if (method != null) {
            return method;
        }

        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(Method m) {
            if (m != null) {
                className = m.getDeclaringClass().getName();
                methodName = m.getName();
                methodRef = new SoftReference(m);
                classRef = new WeakReference(m.getDeclaringClass());
                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 = (Method)methodRef.get();
            if (m == null) {
                Class clazz = (Class)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] = (Class)writeParamTypeRef0.get();
                    if (paramTypes[0] == null) {
                        paramTypes[0] = reLoadClass(writeParamClassNames[0]);
                        if (paramTypes[0] != null) {
                            writeParamTypeRef0 = new WeakReference(paramTypes[0]);
                        }
                    }
                    paramTypes[1] = (Class)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 (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(String name) {

            ClassLoader classLoader = Thread.currentThread().getContextClassLoader();

            // Try the context class loader
            if (classLoader != null) {
                try {
                    return classLoader.loadClass(name);
                } catch (ClassNotFoundException e) {
                    // ignore
                }
            }

            // Try this class's class loader
            classLoader = MappedPropertyDescriptor.class.getClassLoader();
            try {
                return classLoader.loadClass(name);
            } catch (ClassNotFoundException e) {
                return null;
            }
        }
    }
}