SpringMVC18_SpringMVC的数据响应4

一、SpringMVC的数据响应方式

 1) 页面跳转

  • 直接返回字符串
  • 通过ModelAndView对象返回 

 2) 回写数据

  • 直接返回字符串
  • 返回对象或集合

二、页面跳转-返回字符串形式

 直接返回字符串:此种方式会将返回的字符串与视图解析器的前后缀拼接后跳转
  

  重定向不能访问WEB-INF, 重定向的资源必须在可以被访问到的位置。

三、页面跳转-返回ModelAndView形式1

 在Controller中方法返回ModelAndView对象,并且设置视图名称

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick2")
    public ModelAndView save2(){
        /*
            Model:模型,封装数据的
            View:视图,展示数据的
         */
        ModelAndView modelAndView = new ModelAndView();
        //设置模型数据,相当于放到request域中
        modelAndView.addObject("username","zhangsan");
        //设置视图名称,跟视图解析器的前后缀拼接后跳转
        modelAndView.setViewName("success");
        return modelAndView;
    }

}

 success.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>Success!  ${username}</h1>
</body>
</html>

 浏览器访问localhost:8080/user/quick2,视图解析器会转发请求到jsp下的success.jsp文件

       

四、页面跳转-返回ModelAndView形式2

 在Controller中方法形参上直接声明ModelAndView,无需在方法中自己创建,在方法中直接使用该对象设置视图,同样可以跳转页面

 实现1:

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick3")
    //springmvc可以对方法的参数进行注入
    public ModelAndView save3(ModelAndView modelAndView){
        modelAndView.addObject("username","lisi");
        modelAndView.setViewName("success");
        return modelAndView;
    }
}

  浏览器访问localhost:8080/user/quick3,检查浏览器输出

  

 实现2:

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick4")
  //springmvc调用方法时,方法的参数为Model,那么Springmvc会创建一个实际的Model对象  
public String save4(Model model){ model.addAttribute("username","lisan"); return "success"; } }

  浏览器访问localhost:8080/user/quick4,检查浏览器输出

  

五、页面跳转-返回ModelAndView形式3(不常用)

 在Controller方法的形参上可以直接使用原生的HttpServeltRequest对象,只需声明即可,不常用

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick5")
    public String save5(HttpServletRequest httpServletRequest){
        httpServletRequest.setAttribute("username","hanmei");
        return "success";
    }
}

 浏览器访问localhost:8080/user/quick5,检查浏览器输出

 

六、回写数据-直接回写字符串

 Web基础阶段,客户端访问服务器端,如果想直接回写字符串作为响应体返回的话,只需要使用response.getWriter().print(“hello world”)即可,那么在Controller中想直接回写字符串该怎样呢? 

 通过SpringMVC框架注入的response对象,使用response.getWriter().print(“hello world”) 回写数据,此时不需要视图跳转,业务方法返回值为void

 将需要回写的字符串直接返回,但此时需要通过@ResponseBody注解告知SpringMVC框架,方法返回的字符串不是跳转是直接在http响应体中返回

 实现1:

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick6")
    public void save6(HttpServletResponse response) throws IOException {
        response.getWriter().print("hello zhangsan");
    }
}

  浏览器访问localhost:8080/user/quick6,检查浏览器输出

  

 实现2: 

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick7")
    @ResponseBody  //告知SpringMVC框架 不进行视图跳转 直接进行数据响应
    public String save7() throws IOException {
        return "hello lisi";
    }
}

  浏览器访问localhost:8080/user/quick7,检查浏览器输出

  

七、回写数据-直接回写json格式字符串

 实现1: 

package com.itheima.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick8")
    @ResponseBody
    public String save8() throws IOException {
        return "{\"username\":\"zhangsan\",\"age\":18}";
    }
}

  浏览器访问localhost:8080/user/quick8,检查浏览器输出

  

 手动拼接json格式字符串的方式很麻烦,开发中往往要将复杂的java对象转换成json格式的字符串,我们可以使用web阶段学习过的json转换工具jackson进行转换,通过jackson转换json格式字符串,回写字符串

 实现2: 

  pom.xml引入包:

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.14.2</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.14.2</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.14.2</version>
        </dependency>
package com.itheima.domain;

public class User {

    private String username;
    private int age;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", age=" + age +
                '}';
    }
}
package com.itheima.controller;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.itheima.domain.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick9")
    @ResponseBody
    public String save9() throws IOException {
        User user = new User();
        user.setUsername("lisi");
        user.setAge(20);
        //使用json的转换工具将对象转换成json格式字符串再返回
        ObjectMapper objectMapper = new ObjectMapper();
        String json = objectMapper.writeValueAsString(user);
        return json;
    }
}

  浏览器访问localhost:8080/user/quick9,检查浏览器输出

  

八、回写数据-返回对象或集合1

 通过SpringMVC帮助我们对对象或集合进行json字符串的转换并回写,为处理器适配器配置消息转换参数,指定使用jackson进行对象或集合的转换,因此需要在spring-mvc.xml中进行如下配置: 

package com.itheima.controller;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.itheima.domain.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping(value="/quick10")
    @ResponseBody
    //期望SpringMVC自动将User转换成json格式的字符串
    public User save10() {
        User user = new User();
        user.setUsername("lisan");
        user.setAge(21);
        return user;
    }
}

 spring-mvc.xml需要配置处理器适配器,将对象转换成字符串:

    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <property name="messageConverters">
            <list>
                <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />
            </list>
        </property>
    </bean>

 浏览器访问localhost:8080/user/quick10,检查浏览器输出

  

九、回写数据-返回对象或集合2

 在方法上添加@ResponseBody就可以返回json格式的字符串,但是这样配置比较麻烦,配置的代码比较多,因此,我们可以使用mvc的注解驱动代替上述配置

 在SpringMVC的各个组件中,处理器映射器、处理器适配器、视图解析器称为SpringMVC的三大组件。使用<mvc:annotation-driven />自动加载RequestMappingHandlerMapping(处理映射器)和RequestMappingHandlerAdapter(处理适配器),可用在Spring-mvc.xml配置文件中使用<mvc:annotation-driven />替代注解处理器和适配器的配置。 同时使用<mvc:annotation-driven />默认底层就会集成jackson进行对象或集合的json格式字符串的转换

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
                           http://www.springframework.org/schema/mvc https://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <!--Controller的组件扫描-->
    <context:component-scan base-package="com.itheima.controller"/>

    <!--配置内部资源视图解析器-->
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <!-- /jsp/success.jsp -->
        <property name="prefix" value="/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!-- mvc的注解驱动 -->
    <mvc:annotation-driven />

</beans>

 浏览器访问localhost:8080/user/quick10,检查浏览器输出

  

十、知识要点小结

 1) 页面跳转

  • 直接返回字符串
  • 通过ModelAndView对象返回 

 2) 回写数据

  • 直接返回字符串

    HttpServletResponse对象直接写回数据,HttpServletRequest对象带回数据,Model对象带回数据或者@ResponseBody将字符串数据写回

  • 返回对象或集合

    @ResponseBody+<mvc:annotation-driven/>

 

posted on 2023-05-10 18:53  花溪月影  阅读(28)  评论(0编辑  收藏  举报