Question

我正在尝试为Java SE控制台应用程序设置JNDI。

我有以下代码：

public class FooMain {

    public static void main (String args[]) throws NamingException {
        Context context = new InitialContext();
        context.bind("foo", "bar");
    }
}

...并且上下文工厂定义为：

public class MyContextFactory implements InitialContextFactory {

    private static Hashtable store = new Hashtable();

    @Override
    public Context getInitialContext(Hashtable environment) throws NamingException {
        return new InitialContext() {

            @Override
            public void bind(String name, Object obj) {
                store.put(name, obj);
            }

            @Override
            public Object lookup(String name) {
                return store.get(name);
            }    
        };
    }
}

当我使用：

调用我的FooMain课程时

java -Djava.naming.factory.initial=MyContextFactory -cp ... FooMain

我得到无限递归和最终的StackOverflow异常：

Exception in thread "main" java.lang.StackOverflowError
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.naming.internal.VersionHelper12.getContextClassLoader(VersionHelper12.java:185)
at com.sun.naming.internal.ResourceManager.getApplicationResources(ResourceManager.java:549)
at com.sun.naming.internal.ResourceManager.getInitialEnvironment(ResourceManager.java:244)
at javax.naming.InitialContext.init(InitialContext.java:240)
at javax.naming.InitialContext.<init>(InitialContext.java:192)
at MyContextFactory$1.<init>(MyContextFactory.java:20)
at MyContextFactory.getInitialContext(MyContextFactory.java:20)
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:684)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313)
at javax.naming.InitialContext.init(InitialContext.java:244)
at javax.naming.InitialContext.<init>(InitialContext.java:192)
at MyContextFactory$1.<init>(MyContextFactory.java:20)
at MyContextFactory.getInitialContext(MyContextFactory.java:20)
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:684)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313)
at javax.naming.InitialContext.init(InitialContext.java:244)
at javax.naming.InitialContext.<init>(InitialContext.java:192)
at MyContextFactory$1.<init>(MyContextFactory.java:20)
at MyContextFactory.getInitialContext(MyContextFactory.java:20)
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:684)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313)
at javax.naming.InitialContext.init(InitialContext.java:244)
at javax.naming.InitialContext.<init>(InitialContext.java:192)
...

我可以通过创建一个＆＃34;环境来使代码工作。 Hashtable，将MyContextFactory类的名称放在那里（在＆＃34; java.naming.factory.initial＆＃34;键下），然后使用接受Hashtable环境的构造函数创建InitialContext ：

Context context = new InitialContext(environment);

但我的问题是：如何使用no-args构造函数使用＆＃34; -Djava.naming.factory.initial＆＃34;来提供工厂类的名称。在调用JVM时？

Answer 1

感谢Jim Garrison的建议，这就是答案。问题的关键是super(true);类的构造函数中的调用MyContext。

class MyContext extends InitialContext {

    private Hashtable store;

    public MyContext(Hashtable store) throws NamingException {
        super(true);
        this.store = store;
    }

    @Override
    public void bind(String name, Object obj) {
        store.put(name, obj);
    }

    @Override
    public Object lookup(String name) {
        return store.get(name);
    }    

}



public class FooMain {

    private static final int    ANSWER    = 42;
    private static final String JNDI_NAME = "/config/theAnswerToEverything";

    public static void main (String args[]) throws NamingException {
        Context context = new InitialContext();
        putInContext(                    JNDI_NAME, ANSWER);

        int answer = retrieveFromContext(JNDI_NAME);
        Assert.assertEquals(ANSWER, answer);
        System.out.printf("%d\n", answer);
    }


    private static void putInContext(final String key, final Object value) throws NamingException {
        Context context = new InitialContext();
        context.bind(key, value);
    }

    private static int retrieveFromContext(final String key) throws NamingException {
        Context context = new InitialContext();
        return (int) context.lookup(key);
    }
}


public class MyContextFactory implements InitialContextFactory {

    private static Hashtable store = new Hashtable();

    /*
      Do not confuse [store] with [environment]. They serve different
      purposes.
     */

    @Override
    public Context getInitialContext(Hashtable environment) throws NamingException {
        return new MyContext(store);
    }
}

从命令行调用：

$ java -Djava.naming.factory.initial=MyContextFactory -cp [actual classpath] FooMain
42

新的InitialContext（）

1 个答案: