Spring学习(八)——Spring MVC之Restful API返回json数据

在上一篇博客的基础之上，对Spring MVC的使用有了一个基本的了解，而现在基本上都是用的前后端分离，因此需要对上一篇博客的demo进行一些修改，来满足我们的需要。

一、引入jackson依赖

jackson方便直接将Controller中的对象转为json对象返回给前端。

    
    <dependency>
      <groupId>com.fasterxml.jackson.coregroupId>
      <artifactId>jackson-annotationsartifactId>
      <version>2.9.0version>
    dependency>

    <dependency>
      <groupId>com.fasterxml.jackson.coregroupId>
      <artifactId>jackson-databindartifactId>
      <version>2.9.0version>
    dependency>

二、在Controller类中添加注解

方式一：@RestController

可以在Controller类上直接添加@RestController注解，省去@Controller注解，因为@RestController相当于@ResponseBody和@Controller一起的作用效果。在类上添加该注解后，下面的方法默认都将返回的对象转为json字符串。

package cool.gjh.controller;

import cool.gjh.entity.Student;
import cool.gjh.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Controller层
 * 

 *     Restful风格，返回json数据
 * 
 * @author ACE_GJH
 */
@RestController
@RequestMapping("/student")
public class StudentRestfulController {

    @Autowired
    private StudentService studentService;

    @RequestMapping(value = "/data", method = RequestMethod.GET)
    public Map<String, Object> showAll(){

        List<Student> students = studentService.getAllStudent();
        HashMap<String, Object> data = new HashMap<>(4*5/4, 0.8f);
        data.put("code", 200);
        data.put("msg", "OK");
        data.put("data", students);
        data.put("date", System.currentTimeMillis());

        return null;

    }

}

测试效果：

方式二：@ResponseBody

在Controller类的方法上添加@ResponseBody注解，则该方法返回的对象将会以

package cool.gjh.controller;

import cool.gjh.entity.Student;
import cool.gjh.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Controller层
 * 

 *     Restful风格，返回json数据
 * 
 * @author ACE_GJH
 */
@Controller
@RequestMapping("/student")
public class StudentRestfulController {

    @Autowired
    private StudentService studentService;

    @ResponseBody
    @RequestMapping(value = "/data", method = RequestMethod.GET)
    public Map<String, Object> showAll(){

        List<Student> students = studentService.getAllStudent();
        HashMap<String, Object> data = new HashMap<>(4*5/4, 0.8f);
        data.put("code", 200);
        data.put("msg", "OK");
        data.put("data", students);
        data.put("date", System.currentTimeMillis());
        return data;

    }

}

测试效果：