创建JNDI Binding

开发J2EE程序时候，最让人头疼的莫过於各种各样的JNDI Binding，用得最多的一个类型要算DataSource，某些应用服务器上还有邮件服务、目录服务等等。

J2EE程序使用起来十分简单灵活，把服务器安装好然後把J2EE程序上传上去就可以了，比起PHP程序来要简单得多，但是在开发和测试时就要遇到各类名目繁多的概念和封装。一些非EJB项目，例如用Spring组织的项目，为了提高速度往往需要用一些静态变量，但是这些静态变量在程序装载和卸除时经常会出现一些奇怪的问题。

解决这些问题颇费周折，最好的方法莫过於把业务逻辑拿到应用服务器之外编写和测试，但是应用服务器一般都自带大量强大的JNDI资源，废弃不用的话产品会丢失不少卖点，将其模拟下来是最好的方法。一个项目甚至项目里的每个模块，在开发前期做好测试计划都是很有必要的，但这个话题太大了，这里写不了，我这里只写一些关於自己创建JNDI Binding的内容。

自己创建JNDI Binding需要建一大堆模型，至少需要InitialContextFactoryBuilder、InitialContextFactory和Context这三个，不可谓不复杂，但是其机制并不繁琐，只是想得周全一些罢了，例子代码如下：

package testjndi;

import java.util.Hashtable;
import javax.naming.Binding;
import javax.naming.Context;
import javax.naming.Name;
import javax.naming.NameClassPair;
import javax.naming.NameParser;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.spi.InitialContextFactory;
import javax.naming.spi.InitialContextFactoryBuilder;
import javax.naming.spi.NamingManager;

/**
 *
 * @author
 */
public class CustomizedInitialContextFactoryBuilder
            implements InitialContextFactoryBuilder {

    public static void initialize() {

        try {

            // 覆盖原先的设置
            NamingManager.setInitialContextFactoryBuilder(
                new CustomizedInitialContextFactoryBuilder());
        }catch(Exception e) {
            e.printStackTrace(System.err);
        }
    }

    public InitialContextFactory createInitialContextFactory
                (Hashtable<?, ?> environment) throws NamingException {

        return new MyCustomizedInitialContextFactory();
    }
    
    private class MyCustomizedInitialContextFactory
            implements InitialContextFactory {

        public Context getInitialContext(Hashtable<?, ?> environment)
                throws NamingException {

            CustomizedContext customizedContext
                    = new CustomizedContext();

            return customizedContext;
        }
    }

    private class CustomizedContext implements Context {

        public Object addToEnvironment(String propName, Object propVal)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void bind(Name name, Object obj) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void bind(String name, Object obj) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void close() throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Name composeName(Name name, Name prefix) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public String composeName(String name, String prefix)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Context createSubcontext(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Context createSubcontext(String name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void destroySubcontext(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void destroySubcontext(String name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Hashtable<?, ?> getEnvironment() throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public String getNameInNamespace() throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NameParser getNameParser(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NameParser getNameParser(String name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NamingEnumeration<NameClassPair> list(Name name)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NamingEnumeration<NameClassPair> list(String name)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NamingEnumeration<Binding> listBindings(Name name)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public NamingEnumeration<Binding> listBindings(String name)
                throws NamingException {
            
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Object lookup(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Object lookup(String name) throws NamingException {

            // 在这里将JNDI名帮定到实际的内容上
            if (name == null) {
                throw new NamingException("Name must not be null.");
            }else if(name.equals("Key")) {
                return "Value";
            }else {
                throw new NamingException("Name \"" + name + "\" not found.");
            }
        }

        public Object lookupLink(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Object lookupLink(String name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void rebind(Name name, Object obj) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void rebind(String name, Object obj) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public Object removeFromEnvironment(String propName)
                throws NamingException {

            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void rename(Name oldName, Name newName) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void rename(String oldName, String newName)
                throws NamingException {
            
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void unbind(Name name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }

        public void unbind(String name) throws NamingException {
            throw new UnsupportedOperationException("Not supported yet.");
        }


    }
}

最後用一段代码验证一下结果：

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        // 启动JNDI资源
        CustomizedInitialContextFactoryBuilder.initialize();

        try {
            InitialContext initialContext = new InitialContext();
            System.out.println(initialContext.lookup("Key"));
        }catch(Exception e) {
            e.printStackTrace(System.err);
        }
    }

    
}

打印出"Value"，结果正确。