在前面的文章中，已經(jīng)學(xué)會(huì)了如何通過(guò)實(shí)例化一個(gè)連接器和容器來(lái)獲得一個(gè)servlet容器，并將連接器和容器相關(guān)聯(lián)；但在前面的文章中只有一個(gè)連接器可用，該連接器服務(wù)8080端口上的HTTP請(qǐng)求，無(wú)法添加另一個(gè)連接器來(lái)服務(wù)諸如HTTPS之類的其他請(qǐng)求；此外，在前面的文章中的應(yīng)用程序中有些缺憾，即缺少一種啟動(dòng)/關(guān)閉servlet容器的機(jī)制。
org.apache.catalina.Server接口的實(shí)例表示Catalina的整個(gè)servlet引擎，囊括了所有的組件；它使用一個(gè)優(yōu)雅的方式來(lái)啟動(dòng)/關(guān)閉整個(gè)系統(tǒng)，不需要再對(duì)連接器和容器分別啟動(dòng)/關(guān)閉（當(dāng)啟動(dòng)Server組件時(shí)，它會(huì)啟動(dòng)其中所有的組件，然后它就無(wú)限期地等待關(guān)閉命令；如果想要關(guān)閉系統(tǒng)，可以向指定端口發(fā)送一條關(guān)閉命令，Server組件接收到關(guān)閉命令后，就會(huì)關(guān)閉其中所有的組件）。
Server組件使用了另一個(gè)組件（即Service組件）來(lái)包含其他組件，如一個(gè)容器組件和一個(gè)或多個(gè)連接器組件。
下面是Server接口的定義
public
interface
Server {
public
String getInfo();
public
NamingResources getGlobalNamingResources();
public
void
setGlobalNamingResources(NamingResources globalNamingResources);
public
int
getPort();
public
void
setPort(
int
port);
public
String getShutdown();
public
void
setShutdown(String shutdown);
public
void
addService(Service service);
public
void
await();
public
Service findService(String name);
public
Service[] findServices();
public
void
removeService(Service service);
public
void
initialize()
throws
LifecycleException;
}
shutdown屬性保存了必須發(fā)送給Server實(shí)例用來(lái)關(guān)閉整個(gè)系統(tǒng)的關(guān)閉命令，port屬性定義了Server組件會(huì)從哪個(gè)端口獲取關(guān)閉命令，可以調(diào)用addService()方法為Server組件添加Service組件，或通過(guò)removeService()方法刪除某個(gè)Service組件，findService()方法將會(huì)返回添加到該Server組件中的所有Service組件，initialize()方法包含在系統(tǒng)啟動(dòng)前要執(zhí)行的一些代碼
?org.apache.catalina.core.StandardServer類是Server接口的標(biāo)準(zhǔn)實(shí)現(xiàn)，介紹這個(gè)類是因?yàn)槲覀儗?duì)其中的關(guān)閉機(jī)制比較感興趣，而這也是這個(gè)類中最重要的特性；該類的許多方法都與新server.xml文件中的服務(wù)器配置的存儲(chǔ)相關(guān)，但這并不是本文的重點(diǎn)。
一個(gè)Server組件可以有多個(gè)Service組件，StandardServer類提供了addService()方法、 removeService()方法和findServices()方法的實(shí)現(xiàn)
StandardServer類有四個(gè)與生命周期相關(guān)的方法，分別是initialize()方法、 start()方法、 stop()方法和await()方法，就像其他組件一樣，可以初始化并啟動(dòng)Server組件，然后調(diào)用await()方法及stop()方法。調(diào)用await()方法后會(huì)一直阻塞住，直到它總8085端口上接收到關(guān)閉命令。當(dāng)await()方法返回時(shí)，會(huì)運(yùn)行stop()方法來(lái)關(guān)閉其下的所有子組件。
Server實(shí)例的initialize()方法用于初始化添加到其中的Service組件，下面是tomcat4中StandardServer類中initialize()方法的實(shí)現(xiàn)
public
void
initialize()
throws
LifecycleException {
if
(initialized)
throw
new
LifecycleException (
sm.getString(
"standardServer.initialize.initialized"
));
initialized
=
true
;
//
Initialize our defined Services
for
(
int
i = 0; i < services.length; i++
) {
services[i].initialize();
}
}
start()方法用于啟動(dòng)Server組件，在StandardServer類的start()方法的實(shí)現(xiàn)中，它會(huì)啟動(dòng)其所有的Service組件，這些Service組件它們逐個(gè)啟動(dòng)所有其他的組件，如連接器組件和servlet容器。
public
void
start()
throws
LifecycleException {
//
Validate and update our current component state
if
(started)
throw
new
LifecycleException
(sm.getString(
"standardServer.start.started"
));
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(BEFORE_START_EVENT,
null
);
lifecycle.fireLifecycleEvent(START_EVENT,
null
);
started
=
true
;
//
Start our defined Services
synchronized
(services) {
for
(
int
i = 0; i < services.length; i++
) {
if
(services[i]
instanceof
Lifecycle)
((Lifecycle) services[i]).start();
}
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(AFTER_START_EVENT,
null
);
}
stop()方法用于關(guān)閉Server組件
public
void
stop()
throws
LifecycleException {
//
Validate and update our current component state
if
(!
started)
throw
new
LifecycleException
(sm.getString(
"standardServer.stop.notStarted"
));
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(BEFORE_STOP_EVENT,
null
);
lifecycle.fireLifecycleEvent(STOP_EVENT,
null
);
started
=
false
;
//
Stop our defined Services
for
(
int
i = 0; i < services.length; i++
) {
if
(services[i]
instanceof
Lifecycle)
((Lifecycle) services[i]).stop();
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(AFTER_STOP_EVENT,
null
);
}
await()方法負(fù)責(zé)停止整個(gè)tomcat部署的機(jī)制
/**
* Wait until a proper shutdown command is received, then return.
*/
public
void
await() {
//
Set up a server socket to wait on
ServerSocket serverSocket =
null
;
try
{
serverSocket
=
new
ServerSocket(port, 1
,
InetAddress.getByName(
"127.0.0.1"
));
}
catch
(IOException e) {
System.err.println(
"StandardServer.await: create[" +
port
+ "]: " +
e);
e.printStackTrace();
System.exit(
1
);
}
//
Loop waiting for a connection and a valid command
while
(
true
) {
//
Wait for the next connection
Socket socket =
null
;
InputStream stream
=
null
;
try
{
socket
=
serverSocket.accept();
socket.setSoTimeout(
10 * 1000);
//
Ten seconds
stream =
socket.getInputStream();
}
catch
(AccessControlException ace) {
System.err.println(
"StandardServer.accept security exception: "
+
ace.getMessage());
continue
;
}
catch
(IOException e) {
System.err.println(
"StandardServer.await: accept: " +
e);
e.printStackTrace();
System.exit(
1
);
}
//
Read a set of characters from the socket
StringBuffer command =
new
StringBuffer();
int
expected = 1024;
//
Cut off to avoid DoS attack
while
(expected <
shutdown.length()) {
if
(random ==
null
)
random
=
new
Random(System.currentTimeMillis());
expected
+= (random.nextInt() % 1024
);
}
while
(expected > 0
) {
int
ch = -1
;
try
{
ch
=
stream.read();
}
catch
(IOException e) {
System.err.println(
"StandardServer.await: read: " +
e);
e.printStackTrace();
ch
= -1
;
}
if
(ch < 32)
//
Control character or EOF terminates loop
break
;
command.append((
char
) ch);
expected
--
;
}
//
Close the socket now that we are done with it
try
{
socket.close();
}
catch
(IOException e) {
;
}
//
Match against our command string
boolean
match =
command.toString().equals(shutdown);
if
(match) {
break
;
}
else
System.err.println(
"StandardServer.await: Invalid command '" +
command.toString()
+ "' received"
);
}
//
Close the server socket and return
try
{
serverSocket.close();
}
catch
(IOException e) {
;
}
}
await()方法創(chuàng)建一個(gè)ServerSocket對(duì)象，監(jiān)聽8085端口，并在while循環(huán)中調(diào)用它的accept()方法，擋在指定端口上接收到消息時(shí)，才會(huì)從accept()方法中返回，然后將接收到的消息與關(guān)閉命令的字符串相比較，相同的話就跳出while循環(huán)，關(guān)閉ServerSocket，否則會(huì)再次循環(huán)，繼續(xù)等待消息。
Service組件是org.apache.catalina.Service接口的實(shí)例，一個(gè)Service組件可以有一個(gè)servlet容器和多個(gè)連接器實(shí)例，可以自由地把連接器實(shí)例添加到Service組件中，所有的連接器都會(huì)與該servlet容器相關(guān)聯(lián)
下面是Service接口的定義
public
interface
Service {
public
Container getContainer();
public
void
setContainer(Container container);
public
String getInfo();
public
String getName();
public
void
setName(String name);
public
Server getServer();
public
void
setServer(Server server);
public
void
addConnector(Connector connector);
public
Connector[] findConnectors();
public
void
removeConnector(Connector connector);
public
void
initialize()
throws
LifecycleException;
}
org.apache.catalina.core.StandardService類是Service接口的標(biāo)準(zhǔn)實(shí)現(xiàn)，StandardService類的initialize()方法用于初始化添加到其中的所有連接器；此外，還實(shí)現(xiàn)了org.apache.catalina.Lifecycle接口，它的start()方法用于啟動(dòng)servlet容器和所有連接器
StandardService實(shí)例中有兩種組件，分別是連接器和servlet容器，其中servlet容器只有一個(gè)，而連接器則可以有多個(gè)，多個(gè)連接器使tomcat可以為多種不同的請(qǐng)求協(xié)議提供服務(wù)。例如，一個(gè)連接器處理HTTP請(qǐng)求，而另一個(gè)可以處理HTTPS請(qǐng)求。
StandardService類使用變量container來(lái)指向一個(gè)Container接口的實(shí)例，使用數(shù)組connectors來(lái)保存所有連接器的引用
private Container container = null;
private Connector connectors[] = new Connector[0];
需要調(diào)用setContainer()方法將servlet容器與Service組件相關(guān)聯(lián)：
public
void
setContainer(Container container) {
Container oldContainer
=
this
.container;
if
((oldContainer !=
null
) && (oldContainer
instanceof
Engine))
((Engine) oldContainer).setService(
null
);
this
.container =
container;
if
((
this
.container !=
null
) && (
this
.container
instanceof
Engine))
((Engine)
this
.container).setService(
this
);
if
(started && (
this
.container !=
null
) &&
(
this
.container
instanceof
Lifecycle)) {
try
{
((Lifecycle)
this
.container).start();
}
catch
(LifecycleException e) {
;
}
}
synchronized
(connectors) {
for
(
int
i = 0; i < connectors.length; i++
)
connectors[i].setContainer(
this
.container);
}
if
(started && (oldContainer !=
null
) &&
(oldContainer
instanceof
Lifecycle)) {
try
{
((Lifecycle) oldContainer).stop();
}
catch
(LifecycleException e) {
;
}
}
//
Report this property change to interested listeners
support.firePropertyChange("container", oldContainer,
this
.container);
}
與Service組件相關(guān)聯(lián)的servlet容器的實(shí)例將被傳給每個(gè)連接器對(duì)象的setContainer()方法，這樣在Service組件中就可以形成每個(gè)連接器和servlet容器之間的關(guān)聯(lián)關(guān)系。
可以調(diào)用addConnector()方法將連接器添加到Service組件中，調(diào)用removeConnector()方法將某個(gè)連接器移除
public
void
addConnector(Connector connector) {
synchronized
(connectors) {
connector.setContainer(
this
.container);
connector.setService(
this
);
Connector results[]
=
new
Connector[connectors.length + 1
];
System.arraycopy(connectors,
0, results, 0
, connectors.length);
results[connectors.length]
=
connector;
connectors
=
results;
if
(initialized) {
try
{
connector.initialize();
}
catch
(LifecycleException e) {
e.printStackTrace(System.err);
}
}
if
(started && (connector
instanceof
Lifecycle)) {
try
{
((Lifecycle) connector).start();
}
catch
(LifecycleException e) {
;
}
}
//
Report this property change to interested listeners
support.firePropertyChange("connector",
null
, connector);
}
}
在上面方法中，會(huì)初始化并啟動(dòng)添加到其中的連接器。
public
void
removeConnector(Connector connector) {
synchronized
(connectors) {
int
j = -1
;
for
(
int
i = 0; i < connectors.length; i++
) {
if
(connector ==
connectors[i]) {
j
=
i;
break
;
}
}
if
(j < 0
)
return
;
if
(started && (connectors[j]
instanceof
Lifecycle)) {
try
{
((Lifecycle) connectors[j]).stop();
}
catch
(LifecycleException e) {
;
}
}
connectors[j].setContainer(
null
);
connector.setService(
null
);
int
k = 0
;
Connector results[]
=
new
Connector[connectors.length - 1
];
for
(
int
i = 0; i < connectors.length; i++
) {
if
(i !=
j)
results[k
++] =
connectors[i];
}
connectors
=
results;
//
Report this property change to interested listeners
support.firePropertyChange("connector", connector,
null
);
}
}
與生命周期相關(guān)的方法包括從Lifecycle接口中實(shí)現(xiàn)的start()方法和stop()方法，在加上initialize()方法，其中initialize()方法會(huì)調(diào)用該Service組件中所有連接器的上initialize()方法：
public
void
initialize()
throws
LifecycleException {
if
(initialized)
throw
new
LifecycleException (
sm.getString(
"standardService.initialize.initialized"
));
initialized
=
true
;
//
Initialize our defined Connectors
synchronized
(connectors) {
for
(
int
i = 0; i < connectors.length; i++
) {
connectors[i].initialize();
}
}
}
start()方法負(fù)責(zé)啟動(dòng)被添加到該Service組件中的連接器和servlet容器：
public
void
start()
throws
LifecycleException {
//
Validate and update our current component state
if
(started) {
throw
new
LifecycleException
(sm.getString(
"standardService.start.started"
));
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(BEFORE_START_EVENT,
null
);
System.out.println
(sm.getString(
"standardService.start.name",
this
.name));
lifecycle.fireLifecycleEvent(START_EVENT,
null
);
started
=
true
;
//
Start our defined Container first
if
(container !=
null
) {
synchronized
(container) {
if
(container
instanceof
Lifecycle) {
((Lifecycle) container).start();
}
}
}
//
Start our defined Connectors second
synchronized
(connectors) {
for
(
int
i = 0; i < connectors.length; i++
) {
if
(connectors[i]
instanceof
Lifecycle)
((Lifecycle) connectors[i]).start();
}
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(AFTER_START_EVENT,
null
);
}
stop()方法用于關(guān)閉與該Service組件相關(guān)聯(lián)的servlet容器和所有連接器
public
void
stop()
throws
LifecycleException {
//
Validate and update our current component state
if
(!
started) {
throw
new
LifecycleException
(sm.getString(
"standardService.stop.notStarted"
));
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(BEFORE_STOP_EVENT,
null
);
lifecycle.fireLifecycleEvent(STOP_EVENT,
null
);
System.out.println
(sm.getString(
"standardService.stop.name",
this
.name));
started
=
false
;
//
Stop our defined Connectors first
synchronized
(connectors) {
for
(
int
i = 0; i < connectors.length; i++
) {
if
(connectors[i]
instanceof
Lifecycle)
((Lifecycle) connectors[i]).stop();
}
}
//
Stop our defined Container second
if
(container !=
null
) {
synchronized
(container) {
if
(container
instanceof
Lifecycle) {
((Lifecycle) container).stop();
}
}
}
//
Notify our interested LifecycleListeners
lifecycle.fireLifecycleEvent(AFTER_STOP_EVENT,
null
);
}
在前面文章的應(yīng)用程序中，通過(guò)按某個(gè)鍵或強(qiáng)制中斷的方式關(guān)閉servlet容器，Stopper類提供了一種更優(yōu)雅的方式來(lái)關(guān)閉Catalina服務(wù)器；此外，它也保證了所有的生命周期組件的stop()方法都能夠調(diào)用。
public
class
Stopper {
public
static
void
main(String[] args) {
//
the following code is taken from the Stop method of
//
the org.apache.catalina.startup.Catalina class
int
port = 8005
;
try
{
Socket socket
=
new
Socket("127.0.0.1"
, port);
OutputStream stream
=
socket.getOutputStream();
String shutdown
= "SHUTDOWN"
;
for
(
int
i = 0; i < shutdown.length(); i++
)
stream.write(shutdown.charAt(i));
stream.flush();
stream.close();
socket.close();
System.out.println(
"The server was successfully shut down."
);
}
catch
(IOException e) {
System.out.println(
"Error. The server has not been started."
);
}
}
}
---------------------------------------------------------------------------?
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