Spring Web MVC注解应用及一些常用方法技巧

古城微笑少年丶 2022-07-13 04:58 79阅读 0赞

## Spring Web MVC注解应用 ##

**a.RequestMappingHanlderMapping组件**  
**@RequestMapping(“/login..do”)**  
该标签用在Controller业务方法前

**b.Controller编写和配置**  
取消了实现Controller接口及方法的约定  
可以允许我们按需要灵活定义业务方法  
public ModelAndView或者String 方法名（根据需要定义 request,response,session）\{\}  
（Controller需要扫描到Spring容器，必须使用@Controller）

还是写例子 hello.jsp  
处理流程是一样的

**Spring配置文件：**

<context:component-scan base-package="Controller"></context:component-scan>
        
    
        <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/"></property>
        <property name="suffix" value=".jsp"></property>
    
        </bean>

**web.xml**

<servlet>
      <servlet-name>springwebmvc</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      
      <init-param>
        <param-name>contextConfigLocation</param-name>  
        <param-value>classpath:applicationContext.xml</param-value>  
    </init-param>
    
      </servlet>
      <servlet-mapping>
      <servlet-name>springwebmvc</servlet-name>
      <url-pattern>*.do</url-pattern>
      </servlet-mapping>

**Controller:**

package Controller;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.servlet.ModelAndView;
    
    @Controller//扫描到Spring容器
    public class toLogonController { 
        @RequestMapping("logon.do")
        public ModelAndView execute(){
            ModelAndView mav = new ModelAndView("hello");
    
    
            return mav;
    
    
        }
    }

**hello.jsp:**

![这里写图片描述][SouthEast]

## 再写下登陆 ##

//进入登陆页面  
/tologin.do  
DispatcherServlet  
Handlermapping  
LoginController  
ViewResolver  
login.jsp

**主要是Controller**  
**可以把多个控制写在一个里面不同的就是请求路径**

package Controller;
    
    import javax.servlet.http.HttpServletRequest;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.servlet.ModelAndView;
    
    @Controller//扫描到Spring容器
    public class toLogonController { 
        @RequestMapping("tologin.do")
        public ModelAndView execute(){
            ModelAndView mav = new ModelAndView("login");
    
    
            return mav;
    
    
        }
    
        @RequestMapping("login.do") 
    public String checkLogin(HttpServletRequest request){
             String username=request.getParameter("username");
             String password=request.getParameter("password");
             if(username.equals("root")&&password.equals("1234")){
                 return "hello";
             }else
    
        return "login";
    }
    
    }

![这里写图片描述][SouthEast 1]

## 1.Controller如何接收请求参数 ##

**a.利用HttpServletRequest**  
**b.利用业务方法参数**  
参数名与请求参数key保持一致  
请求: `login.do?username=xxx`  
Controller中：

public String f1(String username){}

或者利用**@RequetParam(“key”)**

public checkLogin1( @RequetParam(“key”) String username
    ){
    }

然后这个username就有值了。  
**注意：这个@RequetParam(“key”)是在方法参数中写在参数前面的**

**c.利用实体对象参数**

//使用实体对象user接收请求参数
    public String checkLogin2(User user){
    //利用 user来接收参数并获取。
    }
    然后创建一个entity包写入类 User
    public class User implements Serializable(){ 
    //最好写上接口 Serializable 方便以后序列化
    private String username;
    private String password;
    加上set get方法
    }

**少量参数使用b;利用方法参数名保持一致。大量参数使用c；如果客户端表单数据没有格式检查，遇到非字符串使用a；**

## 2.Controller如何向响应jsp传值 ##

**a.利用HttpServletRequest（setAttribute方法）**  
**b.利用ModelAndView 返回一个ModelAndView对象利用**  
`mav.getModel().put()方法` 其实这个Model是个map  
**c.利用ModelMap方法参数**

@RequestMapping(“login3.do”)
    public String checkLogin3( String username String password  ModelMap model){
    //传给jsp值
    //增加一个参数 ModelMap
    model.put(“username”,username);
    //在jsp中用el表达式获取 ${username}
    }

**d.使用@ModelAttribute(“key”)**  
一个是get方法前面，一个方法参数前面

public String checkLogin4(@ModelAttribute(“user”)String username ){}

这么写就直接会帮你传过去。获取就是$\{user\}  
但只能把参数值传过去。  
或者

@ModelAttribute(“user”)
    public String getName(){
    return “tom”
    }
    等价于
    model.put(“user”,getName()); //${user}

**主要用a和c**

## 3.Controller如何使用session ##

public String checkLogin(HttpSession session){
    session.setAttribute(key,value);
    
    }

然后在jsp中获取session内容还是用el表达式

${sessionScope.username}

## 案例：列表显示功能 ##

/list.do  
DispatcherServlet  
HandlerMapping  
ListController(List,传递到list.jsp)  
ViewResolver  
/WEB-INF/list.jsp

**Controller:**

package Controller;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.servlet.http.HttpServletRequest;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import entity.User;
    
    @Controller
    public class ListController { 
        @RequestMapping("list.do")
        public String listController(HttpServletRequest request){
    
            List<User> list =new ArrayList<User>();
            for(int i=0;i<5;i++){
                User user = new User();
                user.setUsername("admin"+i);
                user.setPassword("password"+i);
    
                list.add(user);
    
            }
    
            request.setAttribute("list", list);
    
    
            return "list";
        }
    
    }

**User:**

package entity;
    
    public class User {
    
        private String username;
        private String password;
        public String getUsername() {
            return username;
        }
        public void setUsername(String username) {
            this.username = username;
        }
        public String getPassword() {
            return password;
        }
        public void setPassword(String password) {
            this.password = password;
        }
    
    }

**list.jsp:**

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <base href="<%=basePath%>">
    
        <title>list</title>
    
        <meta http-equiv="pragma" content="no-cache">
        <meta http-equiv="cache-control" content="no-cache">
        <meta http-equiv="expires" content="0">    
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="This is my page">
        
    
      </head>
      <%@page import="entity.*" %>
      <body>
      <h1>list</h1>
      <table>
      <tr>
      <td>id</td>
      <td>username</td>
      <td>password</td>
      </tr>
      <% List<User> list = ( List<User>)request.getAttribute("list"); int i=0; for(User user:list){ i++; String username=user.getUsername(); String password=user.getPassword(); %>
        <tr>
        <td><%=i %></td>
        <td><%=username %></td>
        <td><%=password %></td>
        </tr>
    
        <% } %>
    
      </table>
    
    
      </body>
    </html>

![这里写图片描述][SouthEast 2]

使用jstl标签：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <base href="<%=basePath%>">
    
        <title>list</title>
    
        <meta http-equiv="pragma" content="no-cache">
        <meta http-equiv="cache-control" content="no-cache">
        <meta http-equiv="expires" content="0">    
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="This is my page">
        
    
      </head>
      <%@page import="entity.*" %>
      <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
      <body>
      <h1>list</h1>
      <table>
      <tr>
      <td>id</td>
      <td>username</td>
      <td>password</td>
      </tr>
    
    <c:forEach items="${list}" var="user">
    <tr>
    <td>${user.username}</td>
    <td>${user.password}</td>
    </tr>
    
    </c:forEach>
      </table>
    
    
      </body>
    </html>

[SouthEast]: /images/20220713/49ca3082a0e94a94a8dd7272af1f6737.png
[SouthEast 1]: /images/20220713/d7f6f8f4e7b548679493eac88d620c16.png
[SouthEast 2]: /images/20220713/860ca902f2c048ddb59d0576bbc5f2c9.png