在eclipse中Servlet的排坑

1.结果

建了一个web project ，然后servlet类终于在web.xml映射中被找到，在浏览器中输入

http://localhost:8080/MyServlet2/myserv?name=liuyan&age=22 也终于有了反应

(一开始是打死也找不到web.xml中映射的servlet类，没有理由)

2.简单的开始

在web-inf的lib中要引入相关的servlet包，包在下图中可以找到：

然后在src下建一个包Test

然后新建一个servlet类myserv.java,代码如下:

public class myserv extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public myserv() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		String name = request.getParameter("name");
		String age = request.getParameter("age");
		System.out.println(name + "," + age );
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

3.配置web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>MyServlet2</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>myserv</display-name> 
    <servlet-name>myserv</servlet-name>
    <servlet-class>Test.myserv</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>myserv</servlet-name> 
    <url-pattern>/myserv</url-pattern>
  </servlet-mapping>
</web-app>

4.问题开始出现了

一般这个时候都是restart tomcate 然后去浏览器输入：

http://localhost:8080/MyServlet2/myserv?name=liuyan&age=22

看会不会有网页显示，并在eclipse中有打印信息。

但是在这个地方被坑了很久，打印信息就是一直报错，没有任何理由（说没有找到）

<servlet-class>Test.myserv</servlet-class>

Test.myserv 

你说奇不奇怪！

5.解决办法

1.重建（新建）web项目，改变A中的值，B中选择javaserver开头的。

2.点击eclipse菜单栏的project,然后clean这个web工程，再重启tomcate.(实测有效)

3.右击红框处，然后monitoring把8080打勾，已经打勾的无视这个解决办法

6.安心的在浏览器中输入，并观察eclipse中的打印结果

7.一个servlet例子

myserv.java

public class myserv extends HttpServlet { ////每次代码改变，都要clean一下工程,再重启服务器
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public myserv() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		String name = request.getParameter("name");
		String age = request.getParameter("age");
		System.out.println(name + "," + age );
		response.getWriter().append("Served at: ").append(request.getContextPath()); //servlet返回数据
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		/*//post 这里要新一个servlet，测试用，写在了一起
		String name = request.getParameter("name");
		String age = request.getParameter("age");
		System.out.println(name + "," + age  );*/
		
		/*//poststring 这里要新一个servlet，测试用，写在了一起
		DataInputStream ds = new DataInputStream(request.getInputStream());
		//ServletInputStream is = request.getInputStream();
		StringBuilder sb = new StringBuilder();
		int len = 0;
		byte[] buf = new byte[1024];
		while((len = ds.read(buf)) != -1){
			sb.append(new String(buf , 0 , len , "utf-8")); //获取string并存到sb当中
		}
		System.out.println(sb.toString());*/
		
		/*//post_file 这里要新一个servlet，测试用，写在了一起
		DataInputStream ds = new DataInputStream(request.getInputStream());
		//ServletInputStream is = request.getInputStream();
		//定义file存放的位置
		File file = new File( "C:\\Users\\liuyan\\Desktop" , "liuyan.jpg");
		FileOutputStream fos = new FileOutputStream(file);
		int len = 0;
		byte[] buf = new byte[1024];
		while((len = ds.read(buf)) != -1){
			fos.write(buf, 0, len); //获取string并存到file当中
		}
		fos.flush();
		fos.close();
		System.out.println("file ok");*/
		
		//post file and params 这里要新一个servlet，测试用，写在了一起
		//参数获得
		//不知道
		/*//上传文件
		File file = new File( "C:\\Users\\liuyan\\Desktop" , "imagename.jpg");
		DataInputStream ds = new DataInputStream(request.getInputStream());
		FileOutputStream fos = new FileOutputStream(file);
		int len = 0;
		byte[] buf = new byte[1024];
		while((len = ds.read(buf)) != -1){
			fos.write(buf, 0, len); //获取string并存到file当中
		}
		fos.flush();
		fos.close();
		System.out.println("file ok");*/
		
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>MyServlet2</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet> //如果有多个servlet也要配置在这里
    <description></description>
    <display-name>myserv</display-name>
    <servlet-name>myserv</servlet-name>
    <servlet-class>Test.myserv</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>myserv</servlet-name>
    <url-pattern>/myserv</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>myserv</display-name>
    <servlet-name>myserv</servlet-name>
    <servlet-class>Test.myserv</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>myserv</servlet-name>
    <url-pattern>/myserv</url-pattern>
  </servlet-mapping>
</web-app>