servlet及jsp之间的请求转发

1、servlet间的请求转发

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>servlet-demo</finalName>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>8.1.16.v20140903</version>
        <configuration>
          <scanIntervalSeconds>10</scanIntervalSeconds>
          <connectors>
            <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
              <port>7777</port>
            </connector>
          </connectors>
          <webAppConfig>
            <contextPath>/</contextPath>
          </webAppConfig>
        </configuration>
      </plugin>
    </plugins>
  </build>
pom.xml
package com.test;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/myServlet")
public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("myServlet2");
        requestDispatcher.forward(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet
package com.demo;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/myServlet2")
public class MyServlert2 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.getWriter().write("I am Servlet2");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet2

myServlet和myServlet2在不同的包，但请求转发时不需要使用—— ../ 之类的相对路径，会自动寻找到适合的Servlet

2、servlet转发到jsp

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>servlet-demo</finalName>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>8.1.16.v20140903</version>
        <configuration>
          <scanIntervalSeconds>10</scanIntervalSeconds>
          <connectors>
            <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
              <port>7777</port>
            </connector>
          </connectors>
          <webAppConfig>
            <contextPath>/</contextPath>
          </webAppConfig>
        </configuration>
      </plugin>
    </plugins>
  </build>
pom.xml
package com.test;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/myServlet")
public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/WEB-INF/my.jsp");
        requestDispatcher.forward(request, response);
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet
<html>
<body>
<h2>Hello World! I am Mike</h2>
</body>
</html>
my.jsp

3、jsp里使用java代码转发到servlet

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.2.1</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>servlet-demo</finalName>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>8.1.16.v20140903</version>
        <configuration>
          <scanIntervalSeconds>10</scanIntervalSeconds>
          <connectors>
            <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
              <port>7777</port>
            </connector>
          </connectors>
          <webAppConfig>
            <contextPath>/</contextPath>
          </webAppConfig>
        </configuration>
      </plugin>
    </plugins>
  </build>
pom.xml
<%-- 下面的内容相当于写在service方法里 --%>
<%
    RequestDispatcher requestDispatcher = request.getRequestDispatcher("myServlet");
    requestDispatcher.include(request, response);
%>
my.jsp
package com.test;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet("/myServlet")
public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<p>How are you</p>");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet

4、jsp标准标签请求转发 

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.2.1</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>servlet-demo</finalName>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>8.1.16.v20140903</version>
        <configuration>
          <scanIntervalSeconds>10</scanIntervalSeconds>
          <connectors>
            <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
              <port>7777</port>
            </connector>
          </connectors>
          <webAppConfig>
            <contextPath>/</contextPath>
          </webAppConfig>
        </configuration>
      </plugin>
    </plugins>
  </build>
pom.xml
<%!
    private String name = "Mike Chang";
%>

<%-- 下面的内容相当于写在service方法里 --%>
<p>I am <%= name %></p>
<jsp:include page="myServlet"/>
my.jsp
package com.test;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet("/myServlet")
public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<p>How are you</p>");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet
I am Mike Chang

How are you
输出

5、jsp核心标签库请求转发

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.2.1</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>servlet-demo</finalName>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty-maven-plugin</artifactId>
        <version>8.1.16.v20140903</version>
        <configuration>
          <scanIntervalSeconds>10</scanIntervalSeconds>
          <connectors>
            <connector implementation="org.eclipse.jetty.server.nio.SelectChannelConnector">
              <port>7777</port>
            </connector>
          </connectors>
          <webAppConfig>
            <contextPath>/</contextPath>
          </webAppConfig>
        </configuration>
      </plugin>
    </plugins>
  </build>
pom.xml
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%!
    private String name = "Mike";
%>

<%-- 下面的内容相当于写在service方法里 --%>
<p>I am <%= name %></p>
<c:import url="myServlet"/>
my.jsp
package com.test;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet("/myServlet")
public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println("<p>How are you</p>");
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}
myServlet
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原文地址：https://www.cnblogs.com/Mike_Chang/p/10324904.html