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?通过server.xml文件来分析
<!--?xml version="1.0" encoding="UTF-8" standalone="no"?-->
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<?xml version=‘1.0‘ encoding=‘utf-8‘?>
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-->
<!-- Note:? A "Server" is not itself a "Container", so you may not
???? define subcomponents such as "Valves" at this level.
???? Documentation at /docs/config/server.html
?--> ? ? ? ? ?注意：一个Tomcat容器只能有且只有一个Server元素，它是顶层类元素，可以包含多个Service
<Server port="8005" shutdown="SHUTDOWN">
? ? ?以下是几个监听器
? <!-- Security listener. Documentation at /docs/config/listeners.html
? <Listener className="org.apache.catalina.security.SecurityListener" />
? -->
? <!--APR library loader. Documentation at /docs/apr.html -->
? <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
? <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html -->
? <Listener className="org.apache.catalina.core.JasperListener" />
? <!-- Prevent memory leaks due to use of particular java/javax APIs-->
? <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
? <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
? <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" />
? <!-- Global JNDI resources
?????? Documentation at /docs/jndi-resources-howto.html
? -->
? ? ?全局JNDI资源，多用于配置datasource
? <GlobalNamingResources>
??? <!-- Editable user database that can also be used by
???????? UserDatabaseRealm to authenticate users
??? -->
??? <Resource name="UserDatabase" auth="Container"
????????????? type="org.apache.catalina.UserDatabase"
????????????? description="User database that can be updated and saved"
????????????? factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
????????????? pathname="conf/tomcat-users.xml" />
? </GlobalNamingResources>
? <!-- A "Service" is a collection of one or more "Connectors" that share
?????? a single "Container" Note:? A "Service" is not itself a "Container",
?????? so you may not define subcomponents such as "Valves" at this level.
?????? Documentation at /docs/config/service.html
?? --> ? ?
? ? ?service是一个多个Connector的集合，用来充分利用容器，它的下级不能有service，下面可以有一个Engine和多个Connector
? <Service name="Catalina">
??? <!--The connectors can use a shared executor, you can define one or more named thread pools-->
??? <!--
??? <Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
??????? maxThreads="150" minSpareThreads="4"/>
??? -->
??? <!-- A "Connector" represents an endpoint by which requests are received
???????? and responses are returned. Documentation at :
???????? Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
???????? Java AJP? Connector: /docs/config/ajp.html
???????? APR (HTTP/AJP) Connector: /docs/apr.html
???????? Define a non-SSL HTTP/1.1 Connector on port 8080
??? -->
? ? ?一个Connector代表一个访问点，监听某个端口，接受请求(请求交给指定的Engine处理)和返回应答。有两种Connector,一种是处理Browser的http请求，另一个监听来自其他webService请求(Apache)
??? <Connector port="8080" protocol="HTTP/1.1"
?????????????? connectionTimeout="20000"
?????????????? redirectPort="8443" />
? ? ?下面是使用线程池的Connector例子
??? <!-- A "Connector" using the shared thread pool-->
??? <!--
??? <Connector executor="tomcatThreadPool"
?????????????? port="8080" protocol="HTTP/1.1"
?????????????? connectionTimeout="20000"
?????????????? redirectPort="8443" />
??? -->
??? <!-- Define a SSL HTTP/1.1 Connector on port 8443
???????? This connector uses the JSSE configuration, when using APR, the
???????? connector should be using the OpenSSL style configuration
???????? described in the APR documentation -->
? ? ?这个是利用APR提高Tomcat处理性能和安全性，但是配置复杂
??? <!--
??? <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true"
?????????????? maxThreads="150" scheme="https" secure="true"
?????????????? clientAuth="false" sslProtocol="TLS" />
??? -->
? ? ?接受来自其他WebService请求的Connector
??? <!-- Define an AJP 1.3 Connector on port 8009 -->
??? <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
??? <!-- An Engine represents the entry point (within Catalina) that processes
???????? every request.? The Engine implementation for Tomcat stand alone
???????? analyzes the HTTP headers included with the request, and passes them
???????? on to the appropriate Host (virtual host).
???????? Documentation at /docs/config/engine.html -->
? ? ?负责处理所有Connector的请求，下面可以包含多个Host，每个Host都有不同的域名，Engine有个defaultHost，在没有找到指定域名的host时使用。
?????下面使用的是负载均衡的Engine
??? <!-- You should set jvmRoute to support load-balancing via AJP ie :
??? <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
??? -->
? ? ?
??? <Engine name="Catalina" defaultHost="localhost">
????? <!--For clustering, please take a look at documentation at:
????????? /docs/cluster-howto.html? (simple how to)
????????? /docs/config/cluster.html (reference documentation) -->
? ? ?配置集群
????? <!--
????? <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
????? -->
????? <!-- Use the LockOutRealm to prevent attempts to guess user passwords
?????????? via a brute-force attack -->
????? <Realm className="org.apache.catalina.realm.LockOutRealm">
??????? <!-- This Realm uses the UserDatabase configured in the global JNDI
???????????? resources under the key "UserDatabase".? Any edits
???????????? that are performed against this UserDatabase are immediately
???????????? available for use by the Realm.? -->
??????? <Realm className="org.apache.catalina.realm.UserDatabaseRealm"
?????????????? resourceName="UserDatabase"/>
????? </Realm>
? ? ?Host代表一个虚拟主机，都有自己的域名，每个Host都有多个或者一个webapp，而每个webapp代表一个Context.
? ? ?Context在创建的时候会先根据tomcat的web.xml文件加载servlet然后根据webapp的web.xml文件加载，在得到请求后根据自己的servlet映射表寻找servlet.
????? <Host name="localhost"? appBase="webapps"
??????????? unpackWARs="true" autoDeploy="true">
??????? <!-- SingleSignOn valve, share authentication between web applications
???????????? Documentation at: /docs/config/valve.html -->
??????? <!--
??????? <Valve className="org.apache.catalina.authenticator.SingleSignOn" />
??????? -->
??????? <!-- Access log processes all example.
???????????? Documentation at: /docs/config/valve.html
???????????? Note: The pattern used is equivalent to using pattern="common" -->
??????? <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
?????????????? prefix="localhost_access_log." suffix=".txt"
?????????????? pattern="%h %l %u %t "%r" %s %b" />
????? </Host>
??? </Engine>
? </Service>
</Server>
?
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| 元素名 |
属性 |
说明 |
| Server |
port |
指定端口负责监听Tomcat关闭请求 |
| shutdown |
指定向端口发送命令的字符串 |
| service |
name |
指定servide名字 |
| Connector |
port |
指定服务器需要的端口号，并监听该端口号请求 |
| minProcessors |
服务器启动时最小创建的处理请求的线程数 |
| maxProcessors |
最大的处理请求的线程数 |
| enableLookups |
如果为ture那么调用request.getRemoteHost()时返回DNS查询到的对方主机名。否则返回IP地址 |
| redirectPort |
指定服务器处理http请求收到了SSL传输请求后重定向的端口号 |
| acceptCount |
指定当所有线程都在被使用时，可以放到请求队列中的请求数目，超过该数目就不予处理 |
| connectionTimeout |
连接超时时间ms为单位 |
| Engine |
defaultHost |
指定默认的Host主机名，这个Host必须存在 |
| Context |
docBase |
应用程序路径或者WAR文件路径 |
| path |
URL路径前缀，如：http://localhost:8080/path/… |
| reloadable |
如果为ture，那么如果WEB-INF中的lib或者classes改变了，那么tomcat会自动重新装载程序，而不是重启tomcat |
| Host |
name |
主机名 |
| appBase |
指定应用程序存放路径 |
| unpackWARs |
true则回京war文件自动解压，否则不解压，直接运行 |
| Logger |
className |
指定logger使用的类名，但是必须实现org.apache.catalina.Logger接口 |
| prefix |
指定log文件前缀 |
| suffix |
指定log文件后缀 |
| timestamp |
true则在log文件上加上时间戳 |
| Realm(表示存放用户名密码以及role的数据库) |
className |
? |
| Value(功能跟logger差不多) |
prefix |
指定log文件前缀 |
| ? |
suffix |
指定log文件后缀 |
| ? |
directory |
指定log文件存放位置 |
| ? |
className |
指定Value使用的类名，如用org.apache.catalina.values.AccessLogValue可以记录应用程序的访问信息 |
| ? |
pattern |
? |
?
通过上面的节点嵌套顺序大致可以看出来，Tomcat处理一个请求的顺序：
假设客户端发起一个请求，地址为：http://localhost:8080/test/index.jsp
1、请求发到服务器的8080端口，被正在监听此端口的Connector获取到
2、Connector把收到的请求交给它所在的Service下的Engine处理，并等待回应
3、Engine得到请求，按照路径找到名为localhost的Host，如果没找到，就交给默认的Host处理。
4、Host接收到请求，并匹配路径为/test的Context，如果找不到就交给名为‘ ‘Context处理
5、path为"/test"的Context收到请求，并在自己的映射表中找到/index.jsp对应的servlet
6、构造HttpServletRequest和HttpServletResponse对象，作为参数传给servlet
7、Context把处理后的HttpServletResponse对象传给Host
8、Host把HttpServletResponse对象传给Engine
9、Engine把HttpServletResponse对象传给Connector
10、Connector把HttpServletResponse对象返回给客户端
整个过程结束。
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通过server.xml来了解Tomcat结构及处理请求流程
原文：http://we-are-here.iteye.com/blog/2248689
