beanconfig.java

来自「jsr170接口的java实现。是个apache的开源项目。」· Java 代码 · 共 191 行

/*
 * 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.jackrabbit.core.config;

import org.apache.commons.collections.BeanMap;

import java.util.Iterator;
import java.util.Properties;

/**
 * Bean configuration class. BeanConfig instances contain the class name
 * and property information required to instantiate a class that conforms
 * with the JavaBean conventions.
 */
public class BeanConfig {

    /** The default class loader used by all instances of this class */
    private static ClassLoader DEFAULT_CLASS_LOADER =
        BeanConfig.class.getClassLoader();
    
    /**
     * The current class loader used by this instance to create instances of
     * configured classes.
     */
    private ClassLoader classLoader = getDefaultClassLoader();
    
    /**
     * The class name of the configured bean.
     */
    private final String className;

    /**
     * The initial properties of the configured bean.
     */
    private final Properties properties;

    /**
     * Creates a bean configuration. Note that a copy of the given
     * bean properties is stored as a part of the created configuration
     * object. Thus the caller is free to modify the given properties
     * once the configuration object has been created.
     *
     * @param className class name of the bean
     * @param properties initial properties of the bean
     */
    public BeanConfig(String className, Properties properties) {
        this.className = className;
        this.properties = (Properties) properties.clone();
    }

    /**
     * Copies a bean configuration.
     *
     * @param config the configuration to be copied
     */
    public BeanConfig(BeanConfig config) {
        this(config.getClassName(), config.getParameters());
    }

    /**
     * Returns the class name of the configured bean.
     *
     * @return class name of the bean
     */
    public String getClassName() {
        return className;
    }

    /**
     * Returns the initial properties of the configured bean.
     *
     * @return initial properties of the bean
     */
    public Properties getParameters() {
        return properties;
    }

    /**
     * Creates a new instance of the configured bean class.
     *
     * @return new bean instance
     * @throws ConfigurationException on bean configuration errors
     */
    public Object newInstance() throws ConfigurationException {
        try {
            Class objectClass =
                Class.forName(getClassName(), true, getClassLoader());
            Object object = objectClass.newInstance();
            BeanMap map = new BeanMap(object);
            Iterator iterator = map.keyIterator();
            while (iterator.hasNext()) {
                String name = (String) iterator.next();
                String value = properties.getProperty(name);
                if (value != null) {
                    map.put(name, properties.getProperty(name));
                }
            }
            return object;
        } catch (ClassNotFoundException e) {
            throw new ConfigurationException(
                    "Configured bean implementation class " + getClassName()
                    + " was not found.", e);
        } catch (InstantiationException e) {
            throw new ConfigurationException(
                    "Configured bean implementation class " + getClassName()
                    + " can not be instantiated.", e);
        } catch (IllegalAccessException e) {
            throw new ConfigurationException(
                    "Configured bean implementation class " + getClassName()
                    + " is protected.", e);
        }
    }

    //---------- Configurable class loader support ----------------------------
    
    /**
     * Returns the current <code>ClassLoader</code> used to instantiate objects
     * in the {@link #newInstance()} method.
     * 
     * @see #newInstance()
     * @see #setClassLoader(ClassLoader)
     * @see #getDefaultClassLoader()
     * @see #setDefaultClassLoader(ClassLoader)
     */
    public ClassLoader getClassLoader() {
        return classLoader;
    }
    
    /**
     * Sets the <code>ClassLoader</code> used to instantiate objects in the
     * {@link #newInstance()} method.
     * 
     * @param classLoader The class loader to set on this instance. If this is
     *      <code>null</code> the system class loader will be used, which may
     *      lead to unexpected class loading failures.
     *      
     * @see #newInstance()
     * @see #getClassLoader()
     * @see #getDefaultClassLoader()
     * @see #setDefaultClassLoader(ClassLoader)
     */
    public void setClassLoader(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }
    
    /**
     * Returns the current <code>ClassLoader</code> used for new instances of
     * this class as the loader used to instantiate objects in the
     * {@link #newInstance()} method.
     * 
     * @see #newInstance()
     * @see #getClassLoader()
     * @see #setClassLoader(ClassLoader)
     * @see #setDefaultClassLoader(ClassLoader)
     */
    public static ClassLoader getDefaultClassLoader() {
        return DEFAULT_CLASS_LOADER;
    }
    
    /**
     * Sets the <code>ClassLoader</code> used for new instances of this class as
     * the loader to instantiate objects in the {@link #newInstance()} method.
     * 
     * @param classLoader The class loader to set as the default class loader.
     *      If this is <code>null</code> the system class loader will be used,
     *      which may lead to unexpected class loading failures. 
     *      
     * @see #newInstance()
     * @see #getClassLoader()
     * @see #setClassLoader(ClassLoader)
     * @see #getDefaultClassLoader()
     */
    public static void setDefaultClassLoader(ClassLoader classLoader) {
        DEFAULT_CLASS_LOADER = classLoader;
    }
}