本文接下来介绍tomcat的默认连接器，Tomcat中的默认连接器必须满足以下要求：
-
实现org.apache.catalina.Connector接口
-
负责创建实现org.apache.catalina.Request接口的Request对象
-
负责创建实现org.apache.catalina.Response接口的Response对象
org.apache.catalina.Connector接口最重要的方法是getContainer() 、setContainer()、creatRequest()、 creatResponse()，setContainer()方法用于设置相关联的servlet容器，getContainer()方法获取相关连的servlet容器，creatRequest()方法为http请求创建request对象，creatResponse()方法创建response对象
下面来分析HttpConnector类实现，HttpConnector类同时实现了org.apache.catalina.Connector接口org.apache.catalina.Lifecycle接口（用于生命周期管理）、java.lang.Runnable接口（多线程接口）
在HttpConnector对象的初始化方法initialize()里面，调用私有方法open()，创建ServerSocket实例
private
ServerSocket open()
throws
IOException, KeyStoreException, NoSuchAlgorithmException,
CertificateException, UnrecoverableKeyException,
KeyManagementException
{
//
Acquire the server socket factory for this Connector
ServerSocketFactory factory =
getFactory();
//
If no address is specified, open a connection on all addresses
if
(address ==
null
) {
log(sm.getString(
"httpConnector.allAddresses"
));
try
{
return
(factory.createSocket(port, acceptCount));
}
catch
(BindException be) {
throw
new
BindException(be.getMessage() + ":" +
port);
}
}
//
Open a server socket on the specified address
try
{
InetAddress is
=
InetAddress.getByName(address);
log(sm.getString(
"httpConnector.anAddress"
, address));
try
{
return
(factory.createSocket(port, acceptCount, is));
}
catch
(BindException be) {
throw
new
BindException(be.getMessage() + ":" + address +
":" +
port);
}
}
catch
(Exception e) {
log(sm.getString(
"httpConnector.noAddress"
, address));
try
{
return
(factory.createSocket(port, acceptCount));
}
catch
(BindException be) {
throw
new
BindException(be.getMessage() + ":" +
port);
}
}
}
上面的ServerSocketFactory factory = getFactory()显然是创建ServerSocket实例的工厂，方法如下
/**
* Return the server socket factory used by this Container.
*/
public
ServerSocketFactory getFactory() {
if
(
this
.factory ==
null
) {
synchronized
(
this
) {
this
.factory =
new
DefaultServerSocketFactory();
}
}
return
(
this
.factory);
}
工厂类DefaultServerSocketFactory实现了ServerSocketFactory接口
public
final
class
DefaultServerSocketFactory
implements
ServerSocketFactory {
public
ServerSocket createSocket (
int
port)
throws
IOException, KeyStoreException, NoSuchAlgorithmException,
CertificateException, UnrecoverableKeyException,
KeyManagementException {
return
(
new
ServerSocket(port));
}
public
ServerSocket createSocket (
int
port,
int
backlog)
throws
IOException, KeyStoreException, NoSuchAlgorithmException,
CertificateException, UnrecoverableKeyException,
KeyManagementException {
return
(
new
ServerSocket(port, backlog));
}
public
ServerSocket createSocket (
int
port,
int
backlog,
InetAddress ifAddress)
throws
IOException, KeyStoreException, NoSuchAlgorithmException,
CertificateException, UnrecoverableKeyException,
KeyManagementException {
return
(
new
ServerSocket(port, backlog, ifAddress));
}
}
下面接着分析用于生命周期的start()方法
/**
* Begin processing requests via this Connector.
*
*
@exception
LifecycleException if a fatal startup error occurs
*/
public
void
start()
throws
LifecycleException {
//
Validate and update our current state
if
(started)
throw
new
LifecycleException
(sm.getString(
"httpConnector.alreadyStarted"
));
threadName
= "HttpConnector[" + port + "]"
;
lifecycle.fireLifecycleEvent(START_EVENT,
null
);
started
=
true
;
//
Start our background thread
threadStart();
//
Create the specified minimum number of processors
while
(curProcessors <
minProcessors) {
if
((maxProcessors > 0) && (curProcessors >=
maxProcessors))
break
;
HttpProcessor processor
=
newProcessor();
recycle(processor);
}
}
首先是启动HttpConnector连接器线程，然后是初始化最少数量的HttpProcessor处理器入栈
/**
* Start the background processing thread.
*/
private
void
threadStart() {
log(sm.getString(
"httpConnector.starting"
));
thread
=
new
Thread(
this
, threadName);
thread.setDaemon(
true
);
thread.start();
}
由于HttpConnector连接器实现了java.lang.Runnable接口，我们分析它的run()方法实现
/**
* The background thread that listens for incoming TCP/IP connections and
* hands them off to an appropriate processor.
*/
public
void
run() {
//
Loop until we receive a shutdown command
while
(!
stopped) {
//
Accept the next incoming connection from the server socket
Socket socket =
null
;
try
{
//
if (debug >= 3)
//
log("run: Waiting on serverSocket.accept()");
socket =
serverSocket.accept();
//
if (debug >= 3)
//
log("run: Returned from serverSocket.accept()");
if
(connectionTimeout > 0
)
socket.setSoTimeout(connectionTimeout);
socket.setTcpNoDelay(tcpNoDelay);
}
catch
(AccessControlException ace) {
log(
"socket accept security exception"
, ace);
continue
;
}
catch
(IOException e) {
//
if (debug >= 3)
//
log("run: Accept returned IOException", e);
try
{
//
If reopening fails, exit
synchronized
(threadSync) {
if
(started && !
stopped)
log(
"accept error: "
, e);
if
(!
stopped) {
//
if (debug >= 3)
//
log("run: Closing server socket");
serverSocket.close();
//
if (debug >= 3)
//
log("run: Reopening server socket");
serverSocket =
open();
}
}
//
if (debug >= 3)
//
log("run: IOException processing completed");
}
catch
(IOException ioe) {
log(
"socket reopen, io problem: "
, ioe);
break
;
}
catch
(KeyStoreException kse) {
log(
"socket reopen, keystore problem: "
, kse);
break
;
}
catch
(NoSuchAlgorithmException nsae) {
log(
"socket reopen, keystore algorithm problem: "
, nsae);
break
;
}
catch
(CertificateException ce) {
log(
"socket reopen, certificate problem: "
, ce);
break
;
}
catch
(UnrecoverableKeyException uke) {
log(
"socket reopen, unrecoverable key: "
, uke);
break
;
}
catch
(KeyManagementException kme) {
log(
"socket reopen, key management problem: "
, kme);
break
;
}
continue
;
}
//
Hand this socket off to an appropriate processor
HttpProcessor processor =
createProcessor();
if
(processor ==
null
) {
try
{
log(sm.getString(
"httpConnector.noProcessor"
));
socket.close();
}
catch
(IOException e) {
;
}
continue
;
}
//
if (debug >= 3)
//
log("run: Assigning socket to processor " + processor);
processor.assign(socket);
//
The processor will recycle itself when it finishes
}
//
Notify the threadStop() method that we have shut ourselves down
//
if (debug >= 3)
//
log("run: Notifying threadStop() that we have shut down");
synchronized
(threadSync) {
threadSync.notifyAll();
}
}
上面方法中，监听客户端的http请求，当监听到http请求时，获取Socket实例，然后委派给HttpProcessor对象进行处理（处理器线程吧），最后是如果收到停止连接器线程命令， 则事件通知可以停止线程了
在上面我们还没有来得及分析HttpProcessor对象的初始化相关，所以要重新回到start()方法（源码分析有时要跟踪方法中对多个其他方法的调用，深度优先则顾此失彼，难以兼顾；而广度优先则不便纵向深入）
//
Create the specified minimum number of processors
while
(curProcessors <
minProcessors) {
if
((maxProcessors > 0) && (curProcessors >=
maxProcessors))
break
;
HttpProcessor processor
=
newProcessor();
recycle(processor);
}
这里是创建最少数量的HttpProcessor处理器并入栈，我们先分析newProcessor()方法的实现
/**
* Create and return a new processor suitable for processing HTTP
* requests and returning the corresponding responses.
*/
private
HttpProcessor newProcessor() {
//
if (debug >= 2)
//
log("newProcessor: Creating new processor");
HttpProcessor processor =
new
HttpProcessor(
this
, curProcessors++
);
if
(processor
instanceof
Lifecycle) {
try
{
((Lifecycle) processor).start();
}
catch
(LifecycleException e) {
log(
"newProcessor"
, e);
return
(
null
);
}
}
created.addElement(processor);
return
(processor);
}
我们可以看到，这里主要是实例化HttpProcessor对象，传入HttpConnector实例本身（里面要用到HttpConnector对象的创建Request对象方法和创建Response对象方法），然后向上转型为Lifecycle接口类型，并调用它的start()方法，接着Vector created = new Vector()成员变量添加该HttpProcessor对象（Vector实现List接口，内部采用数组实现，其操作方法支持线程同步），最后返回实例
/**
* Recycle the specified Processor so that it can be used again.
*
*
@param
processor The processor to be recycled
*/
void
recycle(HttpProcessor processor) {
//
if (debug >= 2)
//
log("recycle: Recycling processor " + processor);
processors.push(processor);
}
这里将HttpProcessor对象入栈，成员变量Stack processors = new Stack()继承自 Vector ，是一种先进后出的数据结构
我们现在来分析run()方法里面的相关源码，也许更容易理解
/**
* Create (or allocate) and return an available processor for use in
* processing a specific HTTP request, if possible. If the maximum
* allowed processors have already been created and are in use, return
* <code>null</code> instead.
*/
private
HttpProcessor createProcessor() {
synchronized
(processors) {
if
(processors.size() > 0
) {
//
if (debug >= 2)
//
log("createProcessor: Reusing existing processor");
return
((HttpProcessor) processors.pop());
}
if
((maxProcessors > 0) && (curProcessors <
maxProcessors)) {
//
if (debug >= 2)
//
log("createProcessor: Creating new processor");
return
(newProcessor());
}
else
{
if
(maxProcessors < 0
) {
//
if (debug >= 2)
//
log("createProcessor: Creating new processor");
return
(newProcessor());
}
else
{
//
if (debug >= 2)
//
log("createProcessor: Cannot create new processor");
return
(
null
);
}
}
}
}
这里是从Stack processors = new Stack()成员变量里面获取HttpProcessor对象 ，后面的代码不用多加解释了吧，你懂的！
后面那段代码是干嘛的
//
Notify the threadStop() method that we have shut ourselves down
//
if (debug >= 3)
//
log("run: Notifying threadStop() that we have shut down");
synchronized
(threadSync) {
threadSync.notifyAll();
}
我们看到threadStop()方法里面的代码，可以看出上面的代码块是用来通知线程停止的
/**
* Stop the background processing thread.
*/
private
void
threadStop() {
log(sm.getString(
"httpConnector.stopping"
));
stopped
=
true
;
try
{
threadSync.wait(
5000
);
}
catch
(InterruptedException e) {
;
}
thread
=
null
;
}
由于HttpProcessor处理器类的源码分析相对独立，加上篇幅还比较多，因此本文先到这里，下文继续……
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