Spring REST JSON 响应示例

1. Spring REST JSON – @ResponseBody注解
- 1.1. JSON 运行时依赖
- 1.2. @ResponseBody支持
2. Spring REST JSON – MappingJackson2JsonView支持
- 2.1. Maven 依赖
- 2.2. 添加MappingJackson2JsonView视图
  - 2.2.1. 控制器变更
  - 2.2.2. 配置变更
4. Spring REST JSON 示例 – 项目结构

原文： https://howtodoinjava.com/spring-restful/spring-rest-hello-world-json-example/

在 Spring REST JSON 示例中，我们将学习编写能够返回资源的 JSON 表示形式的 RESTful Web 服务。我们将使用MappingJackson2JsonView将视图解析为 JSON 正文。

阅读更多： Spring REST XML 教程

1. Spring REST JSON – `@ResponseBody`注解

此首要技术简单易行。我们只需要在应用程序的类路径中包含 jackson 依赖项，spring 就会自动将Jackson2JsonMessageConverter类注册到上下文中。每当我们从 REST API 请求资源并提供 http 标头accept: application/json时，我们都将取回资源的 json 表示形式。

1.1. JSON 运行时依赖

pom.xml

<!-- Jackson JSON Processor -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.4.1</version>
</dependency>

1.2. `@ResponseBody`支持

这里@RestController = @Controller + @ResponseBody

EmployeeRESTController.java

@RestController
public class EmployeeRESTController
{
    @RequestMapping(value = "/employees")
    public EmployeeListVO getAllEmployees()
    {
        EmployeeListVO employees = new EmployeeListVO();
        EmployeeVO empOne = new EmployeeVO(1,"Lokesh","Gupta","howtodoinjava@gmail.com");
        EmployeeVO empTwo = new EmployeeVO(2,"Amit","Singhal","asinghal@yahoo.com");
        EmployeeVO empThree = new EmployeeVO(3,"Kirti","Mishra","kmishra@gmail.com");
        employees.getEmployees().add(empOne);
        employees.getEmployees().add(empTwo);
        employees.getEmployees().add(empThree);
        return employees;
    }
    @RequestMapping(value = "/employees/{id}")
    public ResponseEntity<EmployeeVO> getEmployeeById (@PathVariable("id") int id)
    {
        if (id <= 3) {
            EmployeeVO employee = new EmployeeVO(1,"Lokesh","Gupta","howtodoinjava@gmail.com");
            return new ResponseEntity<EmployeeVO>(employee, HttpStatus.OK);
        }
        return new ResponseEntity(HttpStatus.NOT_FOUND);
    }
}

2. Spring REST JSON – `MappingJackson2JsonView`支持

这是第二技术。 MappingJackson2JsonView类还取决于类路径中 Jackson JSON 处理器库的存在，因此您无需添加任何其他内容。完整的pom.xml看起来像这样。

2.1. Maven 依赖

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.howtodoinjava.demo</groupId>
  <artifactId>springrestexample</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>springrestexample Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <!-- Spring MVC support -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.1.4.RELEASE</version>
    </dependency>
    <!-- Jackson JSON Processor -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.4.1</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>springrestexample</finalName>
  </build>
</project>

2.2. 添加`MappingJackson2JsonView`视图

使用MappingJackson2JsonView类时，您将需要返回MappingJackson2JsonView类型的视图名称。因此，您将需要更改两个位置。

2.2.1. 控制器变更

您将需要从控制器方法返回视图名称。在我们的例子中，视图名称是jsonTemplate。

package com.howtodoinjava.demo.controller;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import com.howtodoinjava.demo.model.EmployeeListVO;
import com.howtodoinjava.demo.model.EmployeeVO;
@Controller
public class EmployeeRESTController 
{
    private EmployeeListVO getEmployeesCollection()
    {
        EmployeeListVO employees = new EmployeeListVO();
        EmployeeVO empOne = new EmployeeVO(1,"Lokesh","Gupta","howtodoinjava@gmail.com");
        EmployeeVO empTwo = new EmployeeVO(2,"Amit","Singhal","asinghal@yahoo.com");
        EmployeeVO empThree = new EmployeeVO(3,"Kirti","Mishra","kmishra@gmail.com");
        employees.getEmployees().add(empOne);
        employees.getEmployees().add(empTwo);
        employees.getEmployees().add(empThree);
        return employees;
    }
    @RequestMapping(value = "/employees")
    public String getAllEmployeesJSON(Model model) 
    {
        model.addAttribute("employees", getEmployeesCollection());
        return "jsonTemplate";
    }
}

2.2.2. 配置变更

您将需要将视图名称jsonTemplate配置为类型为MappingJackson2JsonView的 bean。并且您将需要配置类型为BeanNameViewResolver的视图解析器。这样，视图名称jsonTemplate将与MappingJackson2JsonView匹配，并且将已解析的 JSON 响应返回给客户端。

RESTConfiguration.java

@Configuration
public class RESTConfiguration 
{
    @Bean
    public View jsonTemplate() {
        MappingJackson2JsonView view = new MappingJackson2JsonView();
        view.setPrettyPrint(true);
        return view;
    }
    @Bean
    public ViewResolver viewResolver() {
        return new BeanNameViewResolver();
    }
}

与上述 java 配置等效的 XML 配置如下。

spring-servlet.xml

<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/ http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <context:component-scan base-package="com.howtodoinjava.demo" />
    <mvc:annotation-driven />
    <!-- JSON Support -->
    <bean name="viewResolver" class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
    <bean name="jsonTemplate" class="org.springframework.web.servlet.view.json.MappingJackson2JsonView"/>
</beans>

3. Spring REST JSON 示例 – 演示

现在，当您点击 URL：http://localhost:8080/springrestexample/employees时，您将得到此结果。

Spring REST JSON 响应示例 - 图1

Spring REST JSON 示例

4. Spring REST JSON 示例 – 项目结构

Spring REST JSON 响应示例 - 图2

Spring REST JSON 示例 – 项目结构

这就是带有 spring mvc 的 spring restful web 服务 json 简单示例的全部内容。将您的问题留在我的评论中。

学习愉快！

1. Spring REST JSON – @ResponseBody注解