dreamvc框架(二),dreamvc的机制
宁浩博
上一篇文章点击打开链接，介绍了dreamvc的ioc容器集成，这一篇文章我将会给大家介绍dreamvc的机制，
大家都知道Struts2是由filter进入，然后进行分发的，而SpringMVC是由servlet进入然后进行分发的！对于不同的应用服务器，Filter的init函数的执行时间是不同的，例如：tomcat会在tomcat启动的时候执行init函数，而weblogic等一些其他的应用服务器则会在该Filter匹配的url被首次请求的时候加载。而且filte会在servlet前运行
dreamvc不想规定开发者必须由servlet进入还是由filte进入，dreamvc实现了两种方法。由开发者可以自由的选择，看下面的xml配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<!-- 配置文件位置，默认为/WEB-INF/applicationContext.xml -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<!-- 上下文Spring监听器 -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!--
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-class>org.majorxie.dreamvc.mvc.dispatcher.DispatcherServlet</servlet-class>
<init-param>
<param-name>container</param-name>
<param-value>org.majorxie.dreamvc.ioc.factory.SpringIocFactory</param-value>
</init-param>
<init-param>
<param-name>CodeEnhancement</param-name>
<param-value>javassist</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping> -->
<filter>
<filter-name>DispatcherFilter</filter-name>
<filter-class>org.majorxie.dreamvc.mvc.dispatcher.DispatcherFilter</filter-class><!-- 选择filter进入，或者选择servlet进入（如上） -->
<init-param>
<param-name>container</param-name>
<param-value>org.majorxie.dreamvc.ioc.factory.SpringIocFactory</param-value><!-- 选择springioc作为ioc容器 -->
</init-param>
<init-param>
<param-name>CodeEnhancement</param-name>
<param-value>SpringAsm</param-value><!-- 选择SpringAsm或者javassist -->
</init-param>
<init-param>
<param-name>template</param-name>
<param-value></param-value><!-- 选择返回模板这里不填自动选择jsp模板 -->
</init-param>
</filter>
<filter-mapping>
<filter-name>DispatcherFilter</filter-name>
<url-pattern>*.do</url-pattern>
</filter-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
package org.majorxie.dreamvc.mvc.dispatcher;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.GenericServlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.majorxie.dreamvc.tag.Contextconfig.DefaultConfigImpl;
/**
* dispatcher类，负责初始化任务
* @author xiezhaodong
* 2014-10-28
*
*/
public class DispatcherServlet extends GenericServlet {
private final Log log=LogFactory.getLog(getClass());
private Dispatcher dispatcher;
public void destroy() {
log.info("distory!!");
super.destroy();
}
@Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
this.dispatcher=new Dispatcher();
DefaultConfigImpl configImpl=new DefaultConfigImpl(config);
dispatcher.init(configImpl);
}
@Override
public void service(ServletRequest arg0, ServletResponse arg1)
throws ServletException, IOException {
HttpServletRequest req=(HttpServletRequest) arg0;
HttpServletResponse resp=(HttpServletResponse) arg1;
String method=req.getMethod();
if ("GET".equals(method) || "POST".equals(method)) {
if(!dispatcher.service(req, resp)){
return;
}
}
}
}
package org.majorxie.dreamvc.mvc.dispatcher;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.majorxie.dreamvc.tag.Contextconfig.DefaultConfigImpl;
/**
* filter进入
* @author xiezhaodong
*2014-10-31
*/
public class DispatcherFilter implements Filter{
private Log log=LogFactory.getLog(getClass());
private Dispatcher dispatcher
;
public void destroy() {
log.info("filter enter destory");
}
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) arg0;
HttpServletResponse resp = (HttpServletResponse) arg1;
String method = req.getMethod();
if ("GET".equals(method) || "POST".equals(method)) {
if (!dispatcher.service(req, resp))
arg2.doFilter(req, resp);
return;
}
}
public void init(FilterConfig arg0) throws ServletException {
this.dispatcher=new Dispatcher();
log.info("filter enter start...");
DefaultConfigImpl config=new DefaultConfigImpl(arg0);
dispatcher.init(config);
}
}package org.majorxie.dreamvc.tag.Contextconfig;
import javax.servlet.ServletContext;
/**
* 2014-10-28
* @author xiezhaodong
*
*/
public interface Config {
/**
* 得到指定了参数
* @return
*/
String getInitParameter(String name);
/**
*
* @return servlet context
*/
ServletContext getServletContext();
}
这个折扣封装了两个方法，一个是得到参数，一个是得到servletCOntext，然后再有一个默认实现，一个简单是组合适配，就完成了filter和servlet不同的适配
package org.majorxie.dreamvc.tag.Contextconfig;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import javax.servlet.FilterConfig;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
/**
* 2014-10-28
* @author xiezhaodong
*配置默认实现
*对象适配
*有3个构造函数,选择需要的构造函数实例化
*servletconfig用于serlvet进入
*filterconfig用于filter进入
*
*/
public class DefaultConfigImpl implements FixableConfig {
private ServletConfig servletConfig;
private FilterConfig filterConfig;
public DefaultConfigImpl(ServletConfig servletConfig) {
this(servletConfig,null);
}
public DefaultConfigImpl(FilterConfig filterConfig) {
this(null,filterConfig);
}
public DefaultConfigImpl(ServletConfig servletConfig,FilterConfig filterConfig) {
this.filterConfig =filterConfig;
this.servletConfig=servletConfig;
}
public String getInitParameter(String name) {
return servletConfig==null?filterConfig.getInitParameter(name):servletConfig.getInitParameter(name);
}
public ServletContext getServletContext() {
return servletConfig==null?filterConfig.getServletContext():servletConfig.getServletContext();
}
@SuppressWarnings("unchecked")
public String[] getInitParameters() {
Enumeration<String> names=servletConfig==null?filterConfig.getInitParameterNames():servletConfig.getInitParameterNames();
List<String> list=new ArrayList<String>();
while(names.hasMoreElements()){
list.add(this.getInitParameter(names.nextElement()));
}
return (String[]) list.toArray();
}
}
终上所述，dreamvc的两个机制用户可以自行选择来实现。下一篇讲解Dispatcher类到底做了写什么
转载请注明出处http://blog.csdn.net/a837199685
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