java - 如何使用 Java Reflection 将协议(protocol)字符串转换为 Spymemcached 协议(protocol)枚举？

Question

我有一个使用 Spymemcached 的 Java 5 应用程序，当我想将协议(protocol)字符串转换为 Enum 对象时遇到问题。让我们看一下以下内容:

1. 枚举协议(protocol)位于 ConnectionFactoryBuilder 类中。

package net.spy.memcached;

...

public class ConnectionFactoryBuilder {

    public enum Protocol {
        TEXT, BINARY

        private Protocol() {
            // compiled code
        }
    }

现在我需要将字符串“TEXT”或“BINARY”转换为上面的 ConnectionFactoryBuilder.Protocol 枚举。我尝试了以下代码，但没有任何效果。

package mypackage;

import java.lang.reflect.Field;

public class Test {

    public static void main(String[] args) throws Exception {

        String protocolString = "TEXT";

        // code 1:
        String protocolClassName1 = "net.spy.memcached.ConnectionFactoryBuilder.Protocol";
        Class protocolType1 = Class.forName(protocolClassName1); 
        // The above line throws: Exception in thread "main" java.lang.ClassNotFoundException: net.spy.memcached.ConnectionFactoryBuilder.Protocol
        Object protocolEnumObject1 = Enum.valueOf(protocolType1, protocolString);


        // code 2:
        Class connectionFactoryBuilderClass2 = Class.forName("net.spy.memcached.ConnectionFactoryBuilder");
        Field protocolField2 = null;
        for (Field f : connectionFactoryBuilderClass2.getDeclaredFields()) {
            System.out.print(f.getName() + ", ");
            if (f.getName().equalsIgnoreCase("Protocol")) {
                protocolField2 = f;
            }
        }
        Class protocolType2 = protocolField2.getType();
        Object protocolEnumObject2 = Enum.valueOf(protocolType2, protocolString);
        // In this approach, i can not get protocol field in that ConnectionFactoryBuilder class, here are output of getDeclaredFields():
        // opQueueFactory, readQueueFactory, writeQueueFactory, transcoder, failureMode, 
        // initialObservers, opFact, locator, opTimeout, isDaemon, shouldOptimize, useNagle, 
        // maxReconnectDelay, readBufSize, hashAlg, authDescriptor, opQueueMaxBlockTime, 
        // timeoutExceptionThreshold, metricType, collector, executorService, authWaitTime, $assertionsDisabled, 

    }

}

请帮忙，谢谢!

Answer 1

好的，我已经找到解决这个问题的方法了。基本上，枚举协议(protocol)是 ConnectionFactoryBuilder 中的嵌套类，因此我需要使用 $ 来定位它。

这里是已解决的代码:

package mypackage;

public class Test {

    public static void main(String[] args) throws Exception {

        String protocolString = "TEXT";

        // code 1:
        // OLD: String protocolClassName1 = "net.spy.memcached.ConnectionFactoryBuilder.Protocol";
        String protocolClassName1 = "net.spy.memcached.ConnectionFactoryBuilder$Protocol";
        Class protocolType1 = Class.forName(protocolClassName1); 
        Object protocolEnumObject1 = Enum.valueOf(protocolType1, protocolString);

        System.out.println(protocolEnumObject1.getClass());
        // class net.spy.memcached.ConnectionFactoryBuilder$Protocol

    }

}