idea新建java web工程,idea写servlet

一. 新建项目

1. 新建项目
   
   注意先选择Java EE版本,然后才能调整web application版本

2. 选择项目路径
   

3. web->WEB-INF下面新建两个文件夹lib和classes
   

4. 点击File->Project Structure
   path页面设置如下,修改为刚才创建的那个classes文件夹
   
   依赖页面导入Tomcat的jar包,下图所示:
   

5. 点击Run->Edit Configuration 或者右上角的Edit Configuration
   
   
   Application context 修改为你的项目的名字

6. 点击右上角启动Tomcat,如果启动成功,将会打开页面http://localhost:8080/TestWeb/
   
   如果启动失败,那么点击右上角的浏览器图标将只能查看jsp源代码
   

二.关于servlet中的url跳转问题

• 方法一: 使用xml控制url

index.jsp

<form method="post" action="servlet/HelloSevlet.do">
    <input type="text" name="username">
    <input type="submit" name="submit" value="提交">
</form>

HelloServlet.java

package com.test.web;

import java.io.IOException;

public class HelloServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {

        response.getWriter().println("测试============");
        System.out.println("测试================");
        String str = request.getParameter("username");
        System.out.println(str);
    }

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {

        doPost(request,response);
    }
}

web.xml

<servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>com.test.web.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/servlet/HelloSevlet.do</url-pattern>
</servlet-mapping>

• 方法二: 使用servlet注解控制url

  每开发一个Servlet，都要在web.xml中配置Servlet才能够使用，这实在是很头疼的事情，所以Servlet3.0之后提供了注解(annotation)，使得不再需要在web.xml文件中进行Servlet的部署描述，简化开发流程

index.jsp

//相对路径
<form method="post" action="servlet/LoginServlet.do">
    <input type="text" name="username" value="">
    <input type="submit" name="submit" value="登录">
  </form>

  <form method="post" action="<%=request.getContextPath()%>/servlet/LoginServlet.do">
    <input type="text" name="username" value="">
    <input type="submit" name="submit" value="登录">
  </form>

  <form method="post" action="${pageContext.request.contextPath}/servlet/LoginServlet.do">
    <input type="text" name="username" value="">
    <input type="submit" name="submit" value="登录">
  </form>

  这三个表单效果一样的

HelloServlet.java

package com.test.web;

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("/servlet/LoginServlet.do")
//或者下面这样子
@WebServlet(name = "LoginServlet" ,
    urlPatterns = {"/servlet/LoginServlet.do"})
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("哈哈"+"===========================");
        String str = request.getParameter("username");
        System.out.println(str);

        response.getWriter().println("hello"+str);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

注意其中的urlPatterns必须要以斜杠开头,表示根目录下面,否则会报错Invalid <url-pattern> [servlet/LoginServlet.do] in servlet mapping和Failed to start component[StandardEngine[Catalina].StandardHost[localhost].StandardContext[/TestWeb]]

三. web项目打包为war格式

1. 点击File -> Project Structure

2. 点击Artifacts , 然后点击加号+ 按照下图设置
   

3. Type选择压缩包的形式archive
   

4. Build
   
   

5. 最后就可以在左侧栏看到了 *.war格式的文件
   

6. 把刚才的*.war重命名一下,然后上传到服务器的tomcat->webapps目录下面即可访问