将从DB read创建的平面Java对象转换为嵌套的Json对象

线程注释作为平面记录存储在数据库中，并带有

commonid

和

ParentCommentId

。如下图所示

    commentId : 1
    userId    : 815
    userFName:Joe
    userLName:Doe
    timeStamp:12345678888
    commentText:""
    parentCommentId:0

    commentId : 2
    userId    : 615
    userFirstName:Ken
    userLastName:Tait
    timeStamp:12345678988
    commentText:"Comment text"
    parentCommentId:1

    commentId : 3
    userId    : 415
    userFirstName:Brain
    userLastName:Dell
    timeStamp:12345678
    commentText:"Comment text"
    parentCommentId:0

我使用以下Java类构建Java对象

公共类注释{
int-commentId；
int用户标识；
字符串userFName；
字符串userLName；
长时间戳；
字符串注释文本；
int-parCommId；
}
列出评论；

我有注释对象的

列表。现在，我必须遍历列表并将注释对象列表转换为嵌套的Json对象。
parCommId==0
的注释对象是顶级注释，其他注释对象（
parCommId！=0
）应嵌套在注释对象的
commentId
下

在上面的示例中，输出应该像下面那样嵌套

    CommentId_1
         CommentId_2
    CommentID_3

按照注释中的建议，让我们在
Comment.class
中添加一个
List
字段

然后，假设DB的输入为：

List<Comment> comments = Arrays.asList(
        new Comment(1, 6, "John", "Snow", 0, "asd", 0),
        new Comment(2, 6, "Tif", "Snow", 0, "asd2", 1),
        new Comment(3, 6, "Yur", "Snow", 0, "asd", 2),
        new Comment(4, 6, "Mrr", "Snow", 0, "asd", 0),
        new Comment(5, 6, "Mrr", "Snow", 0, "asd", 2)
);

您使用的是哪个JSON库？我使用的是JSON simple。com.googlecode.json-simpleStore注释位于
Map
中，以
commentId
为键。在注释中添加一个字段：
列出子项
。然后循环浏览注释映射条目并将子项添加到其父项中-
Comment c；map.get（c.parentId）.children.add（c）Map<Integer, List<Comment>> parentToComments = comments.stream()
            .collect(Collectors.groupingBy(Comment::getParCommId));

comments.forEach(comment -> {
    List<Comment> children = parentToComments.get(comment.getCommentId());
    comment.setChildren(children);
});

ObjectMapper objectMapper = new ObjectMapper();
String commentsJson = objectMapper.writeValueAsString(parentToComments.get(0));

[{
    "commentId": 1,
    "userId": 6,
    "userFName": "John",
    "userLName": "Snow",
    "timeStamp": 0,
    "commentText": "asd",
    "parCommId": 0,
    "children": [{
        "commentId": 2,
        "userId": 6,
        "userFName": "Tif",
        "userLName": "Snow",
        "timeStamp": 0,
        "commentText": "asd2",
        "parCommId": 1,
        "children": [{
            "commentId": 3,
            "userId": 6,
            "userFName": "Yur",
            "userLName": "Snow",
            "timeStamp": 0,
            "commentText": "asd",
            "parCommId": 2,
            "children": null
        }, {
            "commentId": 5,
            "userId": 6,
            "userFName": "Mrr",
            "userLName": "Snow",
            "timeStamp": 0,
            "commentText": "asd",
            "parCommId": 2,
            "children": null
        }]
    }]
}, {
    "commentId": 4,
    "userId": 6,
    "userFName": "Mrr",
    "userLName": "Snow",
    "timeStamp": 0,
    "commentText": "asd",
    "parCommId": 0,
    "children": null
}]