java - SpringFramework ResponseBody 返回具有空值的对象

Question

我有一个 RestController，它将 Film 对象列表发送回用户:

@RestController
@RequestMapping("/view")
public class FilmRestController {

    @RequestMapping(value = "/", method = RequestMethod.GET,  produces = "application/json")
    public @ResponseBody List<Film> getCurrentFilms(){
        FilmInfo filmInfo = new FilmInfo();
        return filmInfo.getCurrentFilms();
    }
}

每个 Film 对象包含两个字符串(标题、导演)和 Actor 列表。所以相当简单的pojo。

当我在 Postman 中执行请求时，我收到以下响应:

[
{
    "title": null,
    "director": null,
    "actors": null
},
{
    "title": null,
    "director": null,
    "actors": null
},
{
    "title": null,
    "director": null,
    "actors": null
},
{
    "title": null,
    "director": null,
    "actors": null
}
]

我一开始以为这是一个小故障，所以我后来编写了以下方法:

@RequestMapping(value = "/getOneFilm", method = RequestMethod.GET,  produces = "application/json")
public @ResponseBody Film getOneFilm(){
    Film film = new Film("The Shawshank Redemption", "Frank Darabont", Arrays.asList("Tim Robbins","Morgan Freeman","Bob Gunton"));
    return film;
}

果然我的回应是:

{
"title": null,
"director": null,
"actors": null
}

根据要求，这是我的电影类(class):

package entities;

import java.util.List;

public class Film {

private String title;
private String director;
private List<String> actors;

public Film(String title, String director, List<String> actors) {
    title = this.title;
    director = this.director;
    actors = this.actors;
}


public String getTitle() {
    return title;
}
public void setTitle(String title) {
    this.title = title;
}
public String getDirector() {
    return director;
}
public void setDirector(String director) {
    this.director = director;
}
public List<String> getActors() {
    return actors;
}
public void setActors(List<String> actors) {
    this.actors = actors;
}
}

是否有原因导致 ResponseBody 无法将我的对象转换为在响应中发回？我应该改变策略并手动执行 JSON 序列化程序吗？我

Answer 1

在构造函数中，您正在更新参数而不是属性:

public Film(String title, String director, List<String> actors) {
    title = this.title;
    director = this.director;
    actors = this.actors;
}

类中的属性保持为空。将其更改为:

public Film(String title, String director, List<String> actors) {
    this.title = title;
    this.director = director;
    this.actors = actors;
}