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Commons Collections example source code file (BeanMap.java)

This example Commons Collections source code file (BeanMap.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 Collections tags/keywords

bean, beanmap, class, clonenotsupportedexception, hashmap, illegalaccessexception, illegalargumentexception, iterator, iterator, javabean, method, method, object, object, reflection, transformer, transformer, util

The Commons Collections BeanMap.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.collections;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

import org.apache.commons.collections.list.UnmodifiableList;
import org.apache.commons.collections.keyvalue.AbstractMapEntry;
import org.apache.commons.collections.set.UnmodifiableSet;

/** 
 * An implementation of Map for JavaBeans which uses introspection to
 * get and put properties in the bean.
 * <p>
 * If an exception occurs during attempts to get or set a property then the
 * property is considered non existent in the Map
 *
 * @since Commons Collections 1.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author James Strachan
 * @author Stephen Colebourne
 * @author Dimiter Dimitrov
 * 
 * @deprecated Identical class now available in commons-beanutils (full jar version).
 * This version is due to be removed in collections v4.0.
 */
public class BeanMap extends AbstractMap implements Cloneable {

    private transient Object bean;

    private transient HashMap readMethods = new HashMap();
    private transient HashMap writeMethods = new HashMap();
    private transient HashMap types = new HashMap();

    /**
     * An empty array.  Used to invoke accessors via reflection.
     */
    public static final Object[] NULL_ARGUMENTS = {};

    /**
     * Maps primitive Class types to transformers.  The transformer
     * transform strings into the appropriate primitive wrapper.
     */
    public static HashMap defaultTransformers = new HashMap();
    
    static {
        defaultTransformers.put( 
            Boolean.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Boolean.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Character.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return new Character( input.toString().charAt( 0 ) );
                }
            }
        );
        defaultTransformers.put( 
            Byte.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Byte.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Short.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Short.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Integer.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Integer.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Long.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Long.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Float.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Float.valueOf( input.toString() );
                }
            }
        );
        defaultTransformers.put( 
            Double.TYPE, 
            new Transformer() {
                public Object transform( Object input ) {
                    return Double.valueOf( input.toString() );
                }
            }
        );
    }
    
    
    // Constructors
    //-------------------------------------------------------------------------

    /**
     * Constructs a new empty <code>BeanMap.
     */
    public BeanMap() {
    }

    /**
     * Constructs a new <code>BeanMap that operates on the 
     * specified bean.  If the given bean is <code>null, then
     * this map will be empty.
     *
     * @param bean  the bean for this map to operate on
     */
    public BeanMap(Object bean) {
        this.bean = bean;
        initialise();
    }

    // Map interface
    //-------------------------------------------------------------------------

    public String toString() {
        return "BeanMap<" + String.valueOf(bean) + ">";
    }
    
    /**
     * Clone this bean map using the following process: 
     *
     * <ul>
     * <li>If there is no underlying bean, return a cloned BeanMap without a
     * bean.
     *
     * <li>Since there is an underlying bean, try to instantiate a new bean of
     * the same type using Class.newInstance().
     * 
     * <li>If the instantiation fails, throw a CloneNotSupportedException
     *
     * <li>Clone the bean map and set the newly instantiated bean as the
     * underlying bean for the bean map.
     *
     * <li>Copy each property that is both readable and writable from the
     * existing object to a cloned bean map.  
     *
     * <li>If anything fails along the way, throw a
     * CloneNotSupportedException.
     *
     * <ul>
     */
    public Object clone() throws CloneNotSupportedException {
        BeanMap newMap = (BeanMap)super.clone();

        if(bean == null) {
            // no bean, just an empty bean map at the moment.  return a newly
            // cloned and empty bean map.
            return newMap;
        }

        Object newBean = null;            
        Class beanClass = null;
        try {
            beanClass = bean.getClass();
            newBean = beanClass.newInstance();
        } catch (Exception e) {
            // unable to instantiate
            throw new CloneNotSupportedException
                ("Unable to instantiate the underlying bean \"" +
                 beanClass.getName() + "\": " + e);
        }
            
        try {
            newMap.setBean(newBean);
        } catch (Exception exception) {
            throw new CloneNotSupportedException
                ("Unable to set bean in the cloned bean map: " + 
                 exception);
        }
            
        try {
            // copy only properties that are readable and writable.  If its
            // not readable, we can't get the value from the old map.  If
            // its not writable, we can't write a value into the new map.
            Iterator readableKeys = readMethods.keySet().iterator();
            while(readableKeys.hasNext()) {
                Object key = readableKeys.next();
                if(getWriteMethod(key) != null) {
                    newMap.put(key, get(key));
                }
            }
        } catch (Exception exception) {
            throw new CloneNotSupportedException
                ("Unable to copy bean values to cloned bean map: " +
                 exception);
        }

        return newMap;
    }

    /**
     * Puts all of the writable properties from the given BeanMap into this
     * BeanMap. Read-only and Write-only properties will be ignored.
     *
     * @param map  the BeanMap whose properties to put
     */
    public void putAllWriteable(BeanMap map) {
        Iterator readableKeys = map.readMethods.keySet().iterator();
        while (readableKeys.hasNext()) {
            Object key = readableKeys.next();
            if (getWriteMethod(key) != null) {
                this.put(key, map.get(key));
            }
        }
    }


    /**
     * This method reinitializes the bean map to have default values for the
     * bean's properties.  This is accomplished by constructing a new instance
     * of the bean which the map uses as its underlying data source.  This
     * behavior for <code>clear() differs from the Map contract in that
     * the mappings are not actually removed from the map (the mappings for a
     * BeanMap are fixed).
     */
    public void clear() {
        if(bean == null) return;

        Class beanClass = null;
        try {
            beanClass = bean.getClass();
            bean = beanClass.newInstance();
        }
        catch (Exception e) {
            throw new UnsupportedOperationException( "Could not create new instance of class: " + beanClass );
        }
    }

    /**
     * Returns true if the bean defines a property with the given name.
     * <p>
     * The given name must be a <code>String; if not, this method
     * returns false. This method will also return false if the bean
     * does not define a property with that name.
     * <p>
     * Write-only properties will not be matched as the test operates against
     * property read methods.
     *
     * @param name  the name of the property to check
     * @return false if the given name is null or is not a <code>String;
     *   false if the bean does not define a property with that name; or
     *   true if the bean does define a property with that name
     */
    public boolean containsKey(Object name) {
        Method method = getReadMethod(name);
        return method != null;
    }

    /**
     * Returns true if the bean defines a property whose current value is
     * the given object.
     *
     * @param value  the value to check
     * @return false  true if the bean has at least one property whose 
     *   current value is that object, false otherwise
     */
    public boolean containsValue(Object value) {
        // use default implementation
        return super.containsValue(value);
    }

    /**
     * Returns the value of the bean's property with the given name.
     * <p>
     * The given name must be a {@link String} and must not be 
     * null; otherwise, this method returns <code>null.
     * If the bean defines a property with the given name, the value of
     * that property is returned.  Otherwise, <code>null is 
     * returned.
     * <p>
     * Write-only properties will not be matched as the test operates against
     * property read methods.
     *
     * @param name  the name of the property whose value to return
     * @return  the value of the property with that name
     */
    public Object get(Object name) {
        if ( bean != null ) {
            Method method = getReadMethod( name );
            if ( method != null ) {
                try {
                    return method.invoke( bean, NULL_ARGUMENTS );
                }
                catch (  IllegalAccessException e ) {
                    logWarn( e );
                }
                catch ( IllegalArgumentException e ) {
                    logWarn(  e );
                }
                catch ( InvocationTargetException e ) {
                    logWarn(  e );
                }
                catch ( NullPointerException e ) {
                    logWarn(  e );
                }
            }
        }
        return null;
    }

    /**
     * Sets the bean property with the given name to the given value.
     *
     * @param name  the name of the property to set
     * @param value  the value to set that property to
     * @return  the previous value of that property
     * @throws IllegalArgumentException  if the given name is null;
     *   if the given name is not a {@link String}; if the bean doesn't
     *   define a property with that name; or if the bean property with
     *   that name is read-only
     */
    public Object put(Object name, Object value) throws IllegalArgumentException, ClassCastException {
        if ( bean != null ) {
            Object oldValue = get( name );
            Method method = getWriteMethod( name );
            if ( method == null ) {
                throw new IllegalArgumentException( "The bean of type: "+ bean.getClass().getName() + " has no property called: " + name );
            }
            try {
                Object[] arguments = createWriteMethodArguments( method, value );
                method.invoke( bean, arguments );

                Object newValue = get( name );
                firePropertyChange( name, oldValue, newValue );
            }
            catch ( InvocationTargetException e ) {
                logInfo( e );
                throw new IllegalArgumentException( e.getMessage() );
            }
            catch ( IllegalAccessException e ) {
                logInfo( e );
                throw new IllegalArgumentException( e.getMessage() );
            }
            return oldValue;
        }
        return null;
    }
                    
    /**
     * Returns the number of properties defined by the bean.
     *
     * @return  the number of properties defined by the bean
     */
    public int size() {
        return readMethods.size();
    }

    
    /**
     * Get the keys for this BeanMap.
     * <p>
     * Write-only properties are <b>not included in the returned set of
     * property names, although it is possible to set their value and to get 
     * their type.
     * 
     * @return BeanMap keys.  The Set returned by this method is not
     *        modifiable.
     */
    public Set keySet() {
        return UnmodifiableSet.decorate(readMethods.keySet());
    }

    /**
     * Gets a Set of MapEntry objects that are the mappings for this BeanMap.
     * <p>
     * Each MapEntry can be set but not removed.
     * 
     * @return the unmodifiable set of mappings
     */
    public Set entrySet() {
        return UnmodifiableSet.decorate(new AbstractSet() {
            public Iterator iterator() {
                return entryIterator();
            }
            public int size() {
              return BeanMap.this.readMethods.size();
            }
        });
    }

    /**
     * Returns the values for the BeanMap.
     * 
     * @return values for the BeanMap.  The returned collection is not
     *        modifiable.
     */
    public Collection values() {
        ArrayList answer = new ArrayList( readMethods.size() );
        for ( Iterator iter = valueIterator(); iter.hasNext(); ) {
            answer.add( iter.next() );
        }
        return UnmodifiableList.decorate(answer);
    }


    // Helper methods
    //-------------------------------------------------------------------------

    /**
     * Returns the type of the property with the given name.
     *
     * @param name  the name of the property
     * @return  the type of the property, or <code>null if no such
     *  property exists
     */
    public Class getType(String name) {
        return (Class) types.get( name );
    }

    /**
     * Convenience method for getting an iterator over the keys.
     * <p>
     * Write-only properties will not be returned in the iterator.
     *
     * @return an iterator over the keys
     */
    public Iterator keyIterator() {
        return readMethods.keySet().iterator();
    }

    /**
     * Convenience method for getting an iterator over the values.
     *
     * @return an iterator over the values
     */
    public Iterator valueIterator() {
        final Iterator iter = keyIterator();
        return new Iterator() {            
            public boolean hasNext() {
                return iter.hasNext();
            }
            public Object next() {
                Object key = iter.next();
                return get(key);
            }
            public void remove() {
                throw new UnsupportedOperationException( "remove() not supported for BeanMap" );
            }
        };
    }

    /**
     * Convenience method for getting an iterator over the entries.
     *
     * @return an iterator over the entries
     */
    public Iterator entryIterator() {
        final Iterator iter = keyIterator();
        return new Iterator() {            
            public boolean hasNext() {
                return iter.hasNext();
            }            
            public Object next() {
                Object key = iter.next();
                Object value = get(key);
                return new MyMapEntry( BeanMap.this, key, value );
            }            
            public void remove() {
                throw new UnsupportedOperationException( "remove() not supported for BeanMap" );
            }
        };
    }


    // Properties
    //-------------------------------------------------------------------------

    /**
     * Returns the bean currently being operated on.  The return value may
     * be null if this map is empty.
     *
     * @return the bean being operated on by this map
     */
    public Object getBean() {
        return bean;
    }

    /**
     * Sets the bean to be operated on by this map.  The given value may
     * be null, in which case this map will be empty.
     *
     * @param newBean  the new bean to operate on
     */
    public void setBean( Object newBean ) {
        bean = newBean;
        reinitialise();
    }

    /**
     * Returns the accessor for the property with the given name.
     *
     * @param name  the name of the property 
     * @return the accessor method for the property, or null
     */
    public Method getReadMethod(String name) {
        return (Method) readMethods.get(name);
    }

    /**
     * Returns the mutator for the property with the given name.
     *
     * @param name  the name of the property
     * @return the mutator method for the property, or null
     */
    public Method getWriteMethod(String name) {
        return (Method) writeMethods.get(name);
    }


    // Implementation methods
    //-------------------------------------------------------------------------

    /**
     * Returns the accessor for the property with the given name.
     *
     * @param name  the name of the property 
     * @return null if the name is null; null if the name is not a 
     * {@link String}; null if no such property exists; or the accessor
     *  method for that property
     */
    protected Method getReadMethod( Object name ) {
        return (Method) readMethods.get( name );
    }

    /**
     * Returns the mutator for the property with the given name.
     *
     * @param name  the name of the 
     * @return null if the name is null; null if the name is not a 
     * {@link String}; null if no such property exists; null if the 
     * property is read-only; or the mutator method for that property
     */
    protected Method getWriteMethod( Object name ) {
        return (Method) writeMethods.get( name );
    }

    /**
     * Reinitializes this bean.  Called during {@link #setBean(Object)}.
     * Does introspection to find properties.
     */
    protected void reinitialise() {
        readMethods.clear();
        writeMethods.clear();
        types.clear();
        initialise();
    }

    private void initialise() {
        if(getBean() == null) return;

        Class  beanClass = getBean().getClass();
        try {
            //BeanInfo beanInfo = Introspector.getBeanInfo( bean, null );
            BeanInfo beanInfo = Introspector.getBeanInfo( beanClass );
            PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
            if ( propertyDescriptors != null ) {
                for ( int i = 0; i < propertyDescriptors.length; i++ ) {
                    PropertyDescriptor propertyDescriptor = propertyDescriptors[i];
                    if ( propertyDescriptor != null ) {
                        String name = propertyDescriptor.getName();
                        Method readMethod = propertyDescriptor.getReadMethod();
                        Method writeMethod = propertyDescriptor.getWriteMethod();
                        Class aType = propertyDescriptor.getPropertyType();

                        if ( readMethod != null ) {
                            readMethods.put( name, readMethod );
                        }
                        if ( writeMethod != null ) {
                            writeMethods.put( name, writeMethod );
                        }
                        types.put( name, aType );
                    }
                }
            }
        }
        catch ( IntrospectionException e ) {
            logWarn(  e );
        }
    }

    /**
     * Called during a successful {@link #put(Object,Object)} operation.
     * Default implementation does nothing.  Override to be notified of
     * property changes in the bean caused by this map.
     *
     * @param key  the name of the property that changed
     * @param oldValue  the old value for that property
     * @param newValue  the new value for that property
     */
    protected void firePropertyChange( Object key, Object oldValue, Object newValue ) {
    }

    // Implementation classes
    //-------------------------------------------------------------------------

    /**
     * Map entry used by {@link BeanMap}.
     */
    protected static class MyMapEntry extends AbstractMapEntry {        
        private BeanMap owner;
        
        /**
         * Constructs a new <code>MyMapEntry.
         *
         * @param owner  the BeanMap this entry belongs to
         * @param key  the key for this entry
         * @param value  the value for this entry
         */
        protected MyMapEntry( BeanMap owner, Object key, Object value ) {
            super( key, value );
            this.owner = owner;
        }

        /**
         * Sets the value.
         *
         * @param value  the new value for the entry
         * @return the old value for the entry
         */
        public Object setValue(Object value) {
            Object key = getKey();
            Object oldValue = owner.get( key );

            owner.put( key, value );
            Object newValue = owner.get( key );
            super.setValue( newValue );
            return oldValue;
        }
    }

    /**
     * Creates an array of parameters to pass to the given mutator method.
     * If the given object is not the right type to pass to the method 
     * directly, it will be converted using {@link #convertType(Class,Object)}.
     *
     * @param method  the mutator method
     * @param value  the value to pass to the mutator method
     * @return an array containing one object that is either the given value
     *   or a transformed value
     * @throws IllegalAccessException if {@link #convertType(Class,Object)}
     *   raises it
     * @throws IllegalArgumentException if any other exception is raised
     *   by {@link #convertType(Class,Object)}
     */
    protected Object[] createWriteMethodArguments( Method method, Object value ) throws IllegalAccessException, ClassCastException {            
        try {
            if ( value != null ) {
                Class[] types = method.getParameterTypes();
                if ( types != null && types.length > 0 ) {
                    Class paramType = types[0];
                    if ( ! paramType.isAssignableFrom( value.getClass() ) ) {
                        value = convertType( paramType, value );
                    }
                }
            }
            Object[] answer = { value };
            return answer;
        }
        catch ( InvocationTargetException e ) {
            logInfo( e );
            throw new IllegalArgumentException( e.getMessage() );
        }
        catch ( InstantiationException e ) {
            logInfo( e );
            throw new IllegalArgumentException( e.getMessage() );
        }
    }

    /**
     * Converts the given value to the given type.  First, reflection is
     * is used to find a public constructor declared by the given class 
     * that takes one argument, which must be the precise type of the 
     * given value.  If such a constructor is found, a new object is
     * created by passing the given value to that constructor, and the
     * newly constructed object is returned.<P>
     *
     * If no such constructor exists, and the given type is a primitive
     * type, then the given value is converted to a string using its 
     * {@link Object#toString() toString()} method, and that string is
     * parsed into the correct primitive type using, for instance, 
     * {@link Integer#valueOf(String)} to convert the string into an
     * <code>int.

* * If no special constructor exists and the given type is not a * primitive type, this method returns the original value. * * @param newType the type to convert the value to * @param value the value to convert * @return the converted value * @throws NumberFormatException if newType is a primitive type, and * the string representation of the given value cannot be converted * to that type * @throws InstantiationException if the constructor found with * reflection raises it * @throws InvocationTargetException if the constructor found with * reflection raises it * @throws IllegalAccessException never * @throws IllegalArgumentException never */ protected Object convertType( Class newType, Object value ) throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException { // try call constructor Class[] types = { value.getClass() }; try { Constructor constructor = newType.getConstructor( types ); Object[] arguments = { value }; return constructor.newInstance( arguments ); } catch ( NoSuchMethodException e ) { // try using the transformers Transformer transformer = getTypeTransformer( newType ); if ( transformer != null ) { return transformer.transform( value ); } return value; } } /** * Returns a transformer for the given primitive type. * * @param aType the primitive type whose transformer to return * @return a transformer that will convert strings into that type, * or null if the given type is not a primitive type */ protected Transformer getTypeTransformer( Class aType ) { return (Transformer) defaultTransformers.get( aType ); } /** * Logs the given exception to <code>System.out. Used to display * warnings while accessing/mutating the bean. * * @param ex the exception to log */ protected void logInfo(Exception ex) { // Deliberately do not use LOG4J or Commons Logging to avoid dependencies System.out.println( "INFO: Exception: " + ex ); } /** * Logs the given exception to <code>System.err. Used to display * errors while accessing/mutating the bean. * * @param ex the exception to log */ protected void logWarn(Exception ex) { // Deliberately do not use LOG4J or Commons Logging to avoid dependencies System.out.println( "WARN: Exception: " + ex ); ex.printStackTrace(); } }

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