Java 使用Jackson将ArrayList中的每个元素保存到新行中

我有一个POJO：

public class Game {

    private String title;

    private Set<String> genres;

    private String size;

    private List<String> screenshots;
}

将对象保存到JSON：

mapper.writeValue（新文件（路径），游戏）

JSON看起来像：

{
  "title" : "Dead Cells",
  "genres" : [ "Action" ],
  "size" : "761M",
  "screenshots" : [ "https://lh3.googleusercontent.com/af9mFH4XinZ7f6dx-Ygm9molYPAcMHhhZyQ0udDBd9S9-44v_VBdeA0rjSlQyJRpQg=w1440-h620-rw", "https://lh3.googleusercontent.com/mo0CZaV_aGflOPB8Tzo697l1WoZuoYUN9TiPMWq0zE29v_I99n1Qg185MfHrU-53nxAG=w1440-h620-rw", "https://lh3.googleusercontent.com/FEiHmVyoT1MU3rbAxSkE_aNDuXBuo3YHQOnqfMAfehS-d4k6CvxuyxpX6KKSbJp3Xv28=w1440-h620-rw", "https://lh3.googleusercontent.com/3Zg_EtwMpt-vWNBTdCNE7hP8M6qeDMq91HKfx70FSJ5tVAsPxHkTYWGiCwvHg5ucMykK=w1440-h620-rw", "https://lh3.googleusercontent.com/A9K6iPYty9IvkzeO_29ONdPAnFFs1BBzk6w-dAf1s5JgpZFMpxc5wpbz07fzovJWxlzO=w1440-h620-rw" ]
}

如您所见，所有屏幕截图都打印成一个字符串，但我希望得到如下结果：

{
  "title" : "Dead Cells",
  "genres" : [ "Action" ],
  "size" : "761M",
  "screenshots" : [ "https://lh3.googleusercontent.com/af9mFH4XinZ7f6dx=w1440-h620-rw", 
                    "https://lh3.googleusercontent.com/I99n1Qg185MfHrU-53nxAG=w1440-h620-rw", 
                    "https://lh3.googleusercontent.com/d4k6CvxuyxpX6KKSbJp3Xv28=w1440-h620-rw", 
                    "https://lh3.googleusercontent.com/wvHg5ucMykK=w1440-h620-rw", 
                  ]
}

---

如何操作？

您可以使用ObjectMapper的writerWithDefaultPrettyPrinter，如下代码所示：

Game game = new Game();
ObjectMapper mapper = new ObjectMapper();
File file = new File("pretty-print.json");
mapper.writerWithDefaultPrettyPrinter().writeValue(file, game);

您的数据输出为：

{
  "title" : "Dead Cells",
  "genres" : [ "Action" ],
  "size" : "761M",
  "screenshots" : [ 
"https://lh3.googleusercontent.com/af9mFH4XinZ7f6dx-Ygm9molYPAcMHhhZyQ0udDBd9S9-44v_VBdeA0rjSlQyJRpQg=w1440-h620-rw", 
"https://lh3.googleusercontent.com/mo0CZaV_aGflOPB8Tzo697l1WoZuoYUN9TiPMWq0zE29v_I99n1Qg185MfHrU-53nxAG=w1440-h620-rw", 
"https://lh3.googleusercontent.com/FEiHmVyoT1MU3rbAxSkE_aNDuXBuo3YHQOnqfMAfehS-d4k6CvxuyxpX6KKSbJp3Xv28=w1440-h620-rw", 
"https://lh3.googleusercontent.com/3Zg_EtwMpt-vWNBTdCNE7hP8M6qeDMq91HKfx70FSJ5tVAsPxHkTYWGiCwvHg5ucMykK=w1440-h620-rw", 
"https://lh3.googleusercontent.com/A9K6iPYty9IvkzeO_29ONdPAnFFs1BBzk6w-dAf1s5JgpZFMpxc5wpbz07fzovJWxlzO=w1440-h620-rw" ]
}

---

您需要删除第二个json的最后一个逗号，以使其正确无误。您会遇到什么问题

{
  "title" : "Dead Cells",
  "genres" : [ "Action" ],
  "size" : "761M",
  "screenshots" : [ 
"https://lh3.googleusercontent.com/af9mFH4XinZ7f6dx-Ygm9molYPAcMHhhZyQ0udDBd9S9-44v_VBdeA0rjSlQyJRpQg=w1440-h620-rw", 
"https://lh3.googleusercontent.com/mo0CZaV_aGflOPB8Tzo697l1WoZuoYUN9TiPMWq0zE29v_I99n1Qg185MfHrU-53nxAG=w1440-h620-rw", 
"https://lh3.googleusercontent.com/FEiHmVyoT1MU3rbAxSkE_aNDuXBuo3YHQOnqfMAfehS-d4k6CvxuyxpX6KKSbJp3Xv28=w1440-h620-rw", 
"https://lh3.googleusercontent.com/3Zg_EtwMpt-vWNBTdCNE7hP8M6qeDMq91HKfx70FSJ5tVAsPxHkTYWGiCwvHg5ucMykK=w1440-h620-rw", 
"https://lh3.googleusercontent.com/A9K6iPYty9IvkzeO_29ONdPAnFFs1BBzk6w-dAf1s5JgpZFMpxc5wpbz07fzovJWxlzO=w1440-h620-rw" ]
}