Java中servlet與tomcat的詳解

這篇文章主要介紹了servlet和tomcat，小編覺得蠻不錯的，現在分享給大家，也給大家做個參考。一起跟著小編過來看看吧

Servlet是什麼
為了能讓Web伺服器與Web應用這兩個不同的軟體系統協作，需要一套標準接口，Servlet就是其中最主要的一個接口。

規定：

Web伺服器可以存取任一Web應用程式中實作Servlet介面的類別。

Web應用程式中用於被Web伺服器動態呼叫的程式碼位於Servlet介面的實作類別中。

SUN公司（現在被Oracle收購了…）制定了Web應用於Web伺服器進行協作的一系列標準Java介面（統稱為Java Servlet API）。

SUN公司也對Web伺服器發布及運行Web應用程式的一些細節做了規約。 SUN公司把這一系列標準Java介面和規約統稱為Servlet規格。

Servlet是一種運行在伺服器上的小插件。

Servlet容器是什麼

#在Servlet規格中，把能夠發布和運行JavaWeb應用程式的Web伺服器稱為Servlet容器，他最主要的特稱是動態執行JavaWeb應用程式中的Servlet實作類別中的程式碼。

Tomcat是什麼

#Tomcat是Servlet容器，同時也是輕量級的Web伺服器。

Apache Server、Microsoft IIS、Apache Tomcat都是Web伺服器。

Tomcat作為Web伺服器時，主要負責實作HTTP傳輸等工作。

Tomcat作為Servlet容器時，主要負責解析Request，產生ServletRequest、ServletResponse，將其傳給對應的Servlet（呼叫service( )方法），再將Servlet的對應結果傳回。

Tomcat組成結構

#Server，代表整個Servlet容器元件，是Tomcat的頂層元素。其中可以包含一到多個Service；

Service，包含一個Engine，以及一到多個Connector；

Connector，代表和客戶端程式實際互動的元件，負責接收客戶請求，以及向客戶回傳回應結果；

Engine，處理同一個Service中所有Connector接收到的客戶請求；

Host，在Engine中可以包含多個Host，每個Host定義了一個虛擬主機，它可以包含一個到多個Web應用程式；

Context，一個Host中可以包含多個Context，每個Context代表了運行在虛擬主機上的單一Web應用。

這些欄位都在conf/server.xml中配置，下面是一段apache tomcat 6.0.36預設的server.xml：

<?xml version=&#39;1.0&#39; encoding=&#39;utf-8&#39;?> 
<!-- 
 Licensed to the Apache Software Foundation (ASF) under one or more 
 contributor license agreements. See the NOTICE file distributed with 
 this work for additional information regarding copyright ownership. 
 The ASF licenses this file to You under the Apache License, Version 2.0 
 (the "License"); you may not use this file except in compliance with 
 the License. You may obtain a copy of the License at 
 
   http://www.apache.org/licenses/LICENSE-2.0 
 
 Unless required by applicable law or agreed to in writing, software 
 distributed under the License is distributed on an "AS IS" BASIS, 
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 See the License for the specific language governing permissions and 
 limitations under the License. 
--> 
<!-- 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 
 --> 
<Server port="8005" shutdown="SHUTDOWN"> 
 
 <!--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" /> 
 <!-- JMX Support for the Tomcat server. Documentation at /docs/non-existent.html --> 
 <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" /> 
 <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> 
 
 <!-- Global JNDI resources 
    Documentation at /docs/jndi-resources-howtohtml 
 --> 
 <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 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 Connector on port 8080 
  --> 
  <Connector port="8080" protocol="HTTP/1.1"  
        connectionTimeout="20000"  
        redirectPort="8443" /> 
  <!-- 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 --> 
  <!-- 
  <Connector port="8443" protocol="HTTP/1" SSLEnabled="true" 
        maxThreads="150" scheme="https" secure="true" 
        clientAuth="false" sslProtocol="TLS" /> 
  --> 
 
  <!-- 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 --> 
 
  <!-- 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) --> 
   <!-- 
   <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> 
   -->     
 
   <!-- The request dumper valve dumps useful debugging information about 
      the request and response data received and sent by Tomcat. 
      Documentation at: /docs/config/valve.html --> 
   <!-- 
   <Valve className="org.apache.catalina.valves.RequestDumperValve"/> 
   --> 
 
   <!-- 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"/> 
 
   <!-- Define the default virtual host 
      Note: XML Schema validation will not work with Xerces 2.2. 
    --> 
   <Host name="localhost" appBase="webapps" 
      unpackWARs="true" autoDeploy="true" 
      xmlValidation="false" xmlNamespaceAware="false"> 
 
    <!-- 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 --> 
    <!-- 
    <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"  
        prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/> 
    --> 
 
   </Host> 
  </Engine> 
 </Service> 
</Server>

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