返回ResponseEntity的JSON

Question

@RequestMapping(value = "so", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
ResponseEntity<String> so() {
    return new ResponseEntity<String>("This is a String", HttpStatus.OK);
}

This is a String

Answer 1

问题的根源在于Spring（通过ResponseEntity、RestController和/或ResponseBody）将使用字符串的内容作为原始响应值，而不是将字符串视为要编码的JSON值。即使控制器方法使用produces=mediatype.application_json_value，也是如此，正如这里的问题所示。

它本质上就像下面的区别：

// yields: This is a String
System.out.println("This is a String");

// yields: "This is a String"
System.out.println("\"This is a String\"");

第一个输出不能解析为JSON，但第二个输出可以。

import com.google.gson.Gson;

@RestController
public class MyController

    private static final Gson gson = new Gson();

    @RequestMapping(value = "so", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    ResponseEntity<String> so() {
        return ResponseEntity.ok(gson.toJson("This is a String"));
    }
}