Java后端返回Json数据

Java后端返回Json数据

Jackson

导包

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.12.1</version>
</dependency>

创建ObjectMapper对象，调用writeValueAsString()方法。

@Controller
public class returnJson {
    @RequestMapping("/hello/json")
    @ResponseBody
    public String rJson() throws JsonProcessingException {
        User user = new User("小小哥布林","1234");
        //jackson
        ObjectMapper objectMapper = new ObjectMapper();
        String str = objectMapper.writeValueAsString(user);
        return str;
    }
}

测试：

数据确实是以Json字符串的形式返回给前端了，但出现了乱码问题。

Json乱码问题解决：

• 方式一：

  @Controller
  public class returnJson {
      //在@RequestMapping中显式的声明返回的是json形式的数据
      @RequestMapping(value="/hello/json",produces="application/json;charset=utf-8")
      @ResponseBody
      public String rJson() throws JsonProcessingException {
          User user = new User("小小哥布林","1234");
          //jackson
          ObjectMapper objectMapper = new ObjectMapper();
          String str = objectMapper.writeValueAsString(user);
          return str;
      }
  }
  
  

测试：

​

• 方式二：

  <!-- 在springMVC配置文件中添加如下配置   -->
  <mvc:annotation-driven>
      <!--JSON乱码问题配置-->
      <mvc:message-converters register-defaults="true">
          <bean class="org.springframework.http.converter.StringHttpMessageConverter">
              <constructor-arg value="utf-8"/>
          </bean>
          <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
              <property name="objectMapper">
                  <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                      <property name="failOnEmptyBeans" value="false"/>
                  </bean>
              </property>
          </bean>
      </mvc:message-converters>
  </mvc:annotation-driven>
  

测试：

​

FastJson

导包

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.75</version>
</dependency>

调用Json类的静态方法

@Controller
public class returnJson {
    @RequestMapping("/hello/json")
    @ResponseBody
    public String rJson() throws JsonProcessingException {
        User user = new User("张三","1234");
        String str = JSON.toJSONString(user);
        return str;
    }
}

测试：

​