第一个JavaWeb应用------源自《Tomcat与Javaweb》_第一个java web应用与扩展-优快云博客

本文链接：https://blog.youkuaiyun.com/yakirzhang/article/details/54883089

helloapp的实践操作

1：下载JDK （安装啥都不需要改）

百度jdk下载
jdk包括了jre所以jdk要好些，
安装过程一直确定即可
添加JAVA_HOME，指向JDK目录
添加PATH，指向JDK的bin目录

2：下载TOMCAT

下载zip然后解压即可
添加CATALINA_HOME，指向安装目录

3：在TOMCAT的webapps里面建立helloapp目录，里面具体包括

/src/mypack/DispatcherServlet.java
/WEB-INF/web.xml
/WEB-INF/classes/mypack/DispatcherServlet.class
/hello.jsp
/login.htm

4 : 为避免有的小伙伴没有代码，贴上代码

//DispatcherServlet.java 文件
package mypack;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;

public class DispatcherServlet extends GenericServlet
{
    private String target ="/hello.jsp";

    public void service(ServletRequest request,ServletResponse response) throws ServletException,IOException
    {
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        request.setAttribute("USER",username);
        request.setAttribute("PASSWORD",password);

        ServletContext context =getServletContext();
        RequestDispatcher dispatcher =context.getRequestDispatcher(target);
        dispatcher.forward(request,response);
    }
}

hello.jsp文件如下：

<html>
<head>
    <title>helloapp</title>
</head>
<body>
    <b>Hello: <%=request.getAttribute("USER") %></b>
</body>
</html>

<html>
<head>
<title>helloapp</title>
</head>
<body>
<form name="loginForm" method="POST" action="dispatcher">
<table>
    <tr>
        <td><div align="right">User Name:</div></td>
        <td><input type="text" name="username"></td>
    </tr>
    <tr>
        <td><div align="right">Password:</div></td>
        <td><input type="password" name="password"></td>
    </tr>
    <tr>
        <td><input type="submit" name="submit" value="submit"></td>
        <td><input type="reset" name="reset" value="reset"></td>
    </tr>
</table>
</form>
</body>
</html>

web.xml

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
  version="4.0"
  metadata-complete="true">

  <display-name>Welcome to Tomcat</display-name>
  <description>
     Welcome to Tomcat
  </description>
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>mypack.DispatcherServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/dispatcher</url-pattern>  
  </servlet-mapping>  
</web-app>

5: 前面提到的DispatcherServlet.class是由DispatcherServlet.java编译而成。cmd转到helloapp的目录
javac -classpatch servlet-api.jar的位置 -sourcepath src -d WEB-INF\classes src\mypack\DispatcherServerlet.java
其中servlet-api.jar的位置在tomcat安装目录的lib里面