APR为JBoss AS加速：实现分析

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APR为JBoss加速主要通过基于APR和JNI（Java Native Interface）的Connector实现。具体包括：Connector、JNI和集成。

Connector

1、 基于APR的HTTP11 Connector实现

org.apache.coyote.http11. Http11NioProcessor

org.apache.coyote.http11. Http11AprProtocol

2、 基于APR的AJP Connector实现

org.apache.coyote.ajp. AjpAprProcessor

org.apache.coyote.ajp. AjpAprProtocol

JNI实现

1、 Connector

Java接口：org.apache.tomcat.jni.Library

C实现：native connector的src目录

2、 SSL

Java接口：org.apache.tomcat.jni.SSL

C实现：native connector的src目录

 

APR集成

1、 JNI库的初始化和清除

APR的初始化通过Server的LifecycleListener接口实现，配置在server.xml中，xml片断如下：

<Server>

 

 <!--APR library loader. Documentation at /docs/apr.html -->

 <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="off" />

……

 

JNI库在Server的Lifecycle的INI_EVENT时进行初始化，在AFTER­_STOP_EVENT时进行清除，具体代码如下：

 

/**

     * Primary entry point for startup and shutdown events.

     *

     * @param event The event that has occurred

     */

    public void lifecycleEvent(LifecycleEvent event) {

 

        if (Lifecycle.INIT_EVENT.equals(event.getType())) {

            aprInitialized = init();

            if (aprInitialized) {

                try {

                    initializeSSL();

                } catch (Throwable t) {

                    if (!log.isDebugEnabled()) {

                        log.info(sm.getString("aprListener.sslInit"));

                    } else {

                        log.debug(sm.getString("aprListener.sslInit"));

                    }

                }

            }

        } else if (Lifecycle.AFTER_STOP_EVENT.equals(event.getType())) {

            if (!aprInitialized) {

                return;

            }

            try {

                terminateAPR();

            } catch (Throwable t) {

                if (!log.isDebugEnabled()) {

                    log.info(sm.getString("aprListener.aprDestroy"));

                } else {

                    log.debug(sm.getString("aprListener.aprDestroy"), t);

                }

            }

        }

 

    }

 

 

2、 Connector选用

 

public Connector(String protocol)

        throws Exception {

        setProtocol(protocol);

        // Instantiate protocol handler

        try {

            Class clazz = Class.forName(protocolHandlerClassName);

            this.protocolHandler = (ProtocolHandler) clazz.newInstance();

        } catch (Exception e) {

            log.error

                (sm.getString

                 ("coyoteConnector.protocolHandlerInstantiationFailed", e));

        }

    }

 

 

    /**

     * Set the Coyote protocol which will be used by the connector.

     *

     * @param protocol The Coyote protocol name

     */

    public void setProtocol(String protocol) {

 

        // Test APR support

        initializeAPR();

 

        if (aprInitialized) {

            if ("HTTP/1.1".equals(protocol)) {

                setProtocolHandlerClassName

                    ("org.apache.coyote.http11.Http11AprProtocol");

            } else if ("AJP/1.3".equals(protocol)) {

                setProtocolHandlerClassName

                    ("org.apache.coyote.ajp.AjpAprProtocol");

            } else if (protocol != null) {

                setProtocolHandlerClassName(protocol);

            } else {

                setProtocolHandlerClassName

                    ("org.apache.coyote.http11.Http11AprProtocol");

            }

        } else {

            if ("HTTP/1.1".equals(protocol)) {

                setProtocolHandlerClassName

                    ("org.apache.coyote.http11.Http11Protocol");

            } else if ("AJP/1.3".equals(protocol)) {

                setProtocolHandlerClassName

                    ("org.apache.jk.server.JkCoyoteHandler");

            } else if (protocol != null) {

                setProtocolHandlerClassName(protocol);

            }

        }

 

    }

 

说明：Connector构造函数调用setProtocol函数设置Connector处理请求的Protocol Handler。在setProtocol函数中，只要能够成功地初始化APR，将使用基于APR的实现的org.apache.coyote.http11.Http11AprProtocol和org.apache.coyote.ajp.AjpAprProtocol作为请求处理的Protocol Handler。