MINA源码分析---协议编码解码器工厂ProtocolCodecFactory接口

1、具体的解码器，编码器需要自己根据协议实现

2、实现协议编码解码器工厂ProtocolCodecFactory接口，在里面主要的工作就是创建解码器，编码器实例，并且返回实例

下面贴出三个接口的源码,读者只需要实现这三个接口即可

package org.apache.mina.filter.codec;

import org.apache.mina.core.session.IoSession;

/**
 * Provides {@link ProtocolEncoder} and {@link ProtocolDecoder} which translates
 * binary or protocol specific data into message object and vice versa.
 * 
负责创建编码和解码器
 * Please refer to参见ReverserProtocolProvider类的实现
 * 
 * ReverserProtocolProvider
 * example.
 *
 */
public interface ProtocolCodecFactory {
    /**
     * Returns a new (or reusable) instance of {@link ProtocolEncoder} which
     * encodes message objects into binary or protocol-specific data.
     */
    ProtocolEncoder getEncoder(IoSession session) throws Exception;

    /**
     * Returns a new (or reusable) instance of {@link ProtocolDecoder} which
     * decodes binary or protocol-specific data into message objects.
     */
    ProtocolDecoder getDecoder(IoSession session) throws Exception;
}

package org.apache.mina.filter.codec;

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.session.IoSession;

/**
 * Decodes binary or protocol-specific data into higher-level message objects.
 * 把二进制流或特定协议的数据解码成更高级别的消息对象
 * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
 * method with read data, and then the decoder implementation puts decoded
 * messages into {@link ProtocolDecoderOutput} by calling
 * {@link ProtocolDecoderOutput#write(Object)}.
 * 

 * Please refer to
 * TextLineDecoder
 * example.
 *
 * @see ProtocolDecoderException
 */
public interface ProtocolDecoder {
    /**
     * Decodes binary or protocol-specific content into higher-level message objects.
     * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
     * method with read data, and then the decoder implementation puts decoded
     * messages into {@link ProtocolDecoderOutput}.
     * 当mina读取数据时会触发这个解码方法,并且把解码后的数据放到ProtocolDecoderOutput中
     * @throws Exception if the read data violated protocol specification
     */
    void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out)
            throws Exception;

    /**
     * Invoked when the specified session is closed当某个会话关闭时被触发.  
     * This method is useful 当某个协议(比如HTTP响应)没有指定消息长度时这个方法很有用。
     * when you deal with the protocol which doesn't specify the length of a message
     * such as HTTP response without content-length header. Implement this
     * method to process the remaining data 
     * 可以实现这个方法去处理decode方法没有处理完全的数据
     * that {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
     * method didn't process completely.
     *
     * @throws Exception if the read data violated protocol specification
     */
    void finishDecode(IoSession session, ProtocolDecoderOutput out)
            throws Exception;

    /**
     * Releases all resources related with this decoder.
     *
     * @throws Exception if failed to dispose all resources
     */
    void dispose(IoSession session) throws Exception;
}

package org.apache.mina.filter.codec;

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.session.IoSession;

/**
 * Encodes higher-level message objects into binary or protocol-specific data.
 * 把高层信息转换成二进制或者特定协议的数据
 * MINA invokes {@link #encode(IoSession, Object, ProtocolEncoderOutput)}
 * method with message which is popped from the session write queue, and then
 * the encoder implementation puts encoded messages (typically {@link IoBuffer}s)
 * into {@link ProtocolEncoderOutput} by calling {@link ProtocolEncoderOutput#write(Object)}.
 * 

 * Please refer to
 * TextLineEncoder
 * example.
 */
public interface ProtocolEncoder {

    /**
     * Encodes higher-level message objects into binary or protocol-specific data.
     * MINA invokes {@link #encode(IoSession, Object, ProtocolEncoderOutput)}
     * method with message which is popped from the session write queue, and then
     * the encoder implementation puts encoded messages (typically {@link IoBuffer}s)
     * into {@link ProtocolEncoderOutput}.
     *
     * @throws Exception if the message violated protocol specification
     */
    void encode(IoSession session, Object message, ProtocolEncoderOutput out)
            throws Exception;

    /**
     * Releases all resources related with this encoder.
     *
     * @throws Exception if failed to dispose all resources
     */
    void dispose(IoSession session) throws Exception;
}