servlet转发、包含详解（七）
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2024-04-01 17:07:40
本文为大家介绍了servlet转发、servlet包含，供大家参考，具体内容如下
1.什么是servlet转发？
servlet将用户的请求通过一组servlet来...
本文为大家介绍了servlet转发、servlet包含，供大家参考，具体内容如下
1.什么是servlet转发？
servlet将用户的请求通过一组servlet来处理，每个servlet都有自己特定的职责，当该servlet完成自己的工作后将请求转发到下一个servlet来处理，这种通过不同servelet相互转发请求来完成对某个请求的处理过程就叫做servlet转发。
2.什么是servlet包含？
servlet包含就是源servlet将其他web组件（servlet，html,jsp）,生成的结果包含到自己的结果中。
3.为什么需要servlet转发和包含？
servlet对象是由servlet容器创建，servlet对象的service（）方法是由servlet容器调用，servlet之间是不允许相互调用（servlet api 2.1以前版本可以）。但是我们又需要通过多个servlet组件协调完成任务，同时方便代码维护管理，提高开发效率。这样就可以需要servlet转发和包含的技术支持。
4、转发和包含的相同点
（1）都是对同一个请求对象处理，源组件和目标组件共享同一个servletrequest对象和servletresponse对象。
（2）目标组件都可以是servlet，jsp，html。
（3）都依赖javax,servlet.requestdispatcher 接口。
5.requestdispatcher 对象
该接口表示请求分发器
（1）获取requestdispatcher对象方法
调用servletcontext的getrequestdispather(string path)方法获得。
调用servletrequest的getrequestdispather(string path)方法获得。
（2）两种方法的区别
servletcontext调用方法的参数必须为绝对路径，而servletrequest调用方法参数可以是绝对路径也可以是相对路径。
6.请求转发案例
checkservlet 类用于处理用户请求参数。
package com.learn;
import javax.servlet.requestdispatcher;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.io.printwriter;
/**
* created by administrator on 2017/09/26.
*/
public class checkservlet extends httpservlet{
@override
protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
string username = req.getparameter("name");
string message = "";
if(username == null){
message = "please input your name";
} else {
message = username;
}
req.setattribute("mess",message);
requestdispatcher requestdispatcher = getservletcontext().getrequestdispatcher("/out");
printwriter out = resp.getwriter();
out.print("before forward ");
system.out.println("before forward");
requestdispatcher.forward(req,resp);
out.print("after forward");
system.out.println("after forward");
out.close();
}
}
outservlet 用于输出处理结果
package com.learn;
import org.json.http;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.io.printwriter;
/**
* created by administrator on 2017/09/26.
*/
public class outservlet extends httpservlet {
@override
protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
string message = (string) req.getattribute("mess");
printwriter printwriter = resp.getwriter();
printwriter.print(message);
printwriter.close();
}
}
注意： 1.在转发之前不要提交响应结果。
2.转发过程中，源组件的响应结果不会返回，只会返回目标组件的响应结果。
web.xml配置
<servlet>
<servlet-name>check</servlet-name>
<servlet-class>com.learn.checkservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>check</servlet-name>
<url-pattern>/check</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>out</servlet-name>
<servlet-class>com.learn.outservlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>out</servlet-name>
<url-pattern>/out</url-pattern>
</servlet-mapping>
7.包含（include）案例
mainservlet 用于包含其他组件，并返回响应结果
package com.learn;
import javax.servlet.requestdispatcher;
import javax.servlet.servlet;
import javax.servlet.servletcontext;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.io.printwriter;
/**
* created by administrator on 2017/09/26.
*/
public class mainservlet extends httpservlet {
@override
protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
resp.setcontenttype("text/html");
printwriter out = resp.getwriter();
out.println("<html><head><title>mainservlet</title></head>");
out.println("<body>");
servletcontext servletcontext = getservletcontext();
requestdispatcher headdispatcher = servletcontext.getrequestdispatcher("/header.html");
requestdispatcher greetdispatcher = servletcontext.getrequestdispatcher("/greet");
requestdispatcher footedispatcher = servletcontext.getrequestdispatcher("/footer.html");
headdispatcher.include(req,resp);
greetdispatcher.include(req,resp);
footedispatcher.include(req,resp);
out.print("</body></html>");
out.close();
}
}
header.html
<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>header</title> </head> <body> <font size="6">welcome to ab</font> </body> </html>
greetservlet
package com.learn;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
import java.io.printwriter;
/**
* created by administrator on 2017/09/26.
*/
public class greetservlet extends httpservlet {
@override
protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception {
printwriter out = resp.getwriter();
out.print("hi! "+req.getparameter("name")+", <p>");
out.close();
}
}
footer.html
<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>footer</title> </head> <body> <span>thanks for stopping</span> </body> </html>
web.xm配置
<servlet> <servlet-name>main</servlet-name> <servlet-class>com.learn.mainservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>main</servlet-name> <url-pattern>/main</url-pattern> </servlet-mapping> <servlet> <servlet-name>greet</servlet-name> <servlet-class>com.learn.greetservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>greet</servlet-name> <url-pattern>/greet</url-pattern> </servlet-mapping>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。