java - 将 JSON 对象映射到 Java 类

Question

我有一个解析为 JSON 的文件系统结构:

{
    "name": "rootf",
    "type": "system",
    "path": "Parsing/rootf",
    "children": [{
        "name": "f1",
        "type": "folder",
        "path": "Parsing/rootf/f1",
        "children": [{
            "name": "subf1",
            "type": "folder",
            "path": "Parsing/rootf/f1/subf1",
            "children": [{
                "name": "text1.txt",
                "type": "file",
                "path": "Parsing/rootf/folder1/subf1/text1.txt",
                "children": ["a", "b", "c"]
            }]
        }, {
            "name": "subf2",
            "type": "folder",
            "path": "Parsing/rootf/f1/subf2",
            "children": []
        }, {
            "name": "text2.txt",
            "type": "file",
            "path": "TParsing/rootf/f1/text2.txt",
            "children": ["d", "e", "f"]
        }]
    }, {
        "name": "text1.txt",
        "type": "file",
        "path": "Parsing/rootd/text1.txt",
        "children": ["aa", "bb"]
    }],
    "_id": "5ce47292d866fc2f40037a56"
}

可以看出children类型 system (表示根文件夹)且类型为 folder (表示根文件夹的子文件夹)可以包含其他文件夹和/或文件。 children类型 file包含文件的内容。

我稍后需要访问 folder 类型的单个对象并输入 file 。将其映射到 Java 对象的最有效方法是什么？我如何单独访问它们？

我最初尝试使用 GSON 将其映射到三个类，System.java , Folder.java和File.java其中包含 private List<Folder> children , private List<File> children和private List<String> children分别。仅当我有特定的 JSON 结构(RootFolder->Sub-Folder->File)时，这才有效。有什么方法可以使映射更加通用，以便它包含 System 的条件可以包含Folder和File类似地，a Folder可以包含Folder和File ？

Answer 1

JSON 中有一个问题，内容如果是文件或文件夹，则表示为 children，因此我尝试了一种替换 children JSON 的方法如果它具有使用正则表达式的字符串集合，其中没有任何 JSON 对象，则使用 file 键。完成后，我只需要一个类，即我的情况下的文件夹，将其解析为 JSON 到 java 类。
所以我的类(class)如下。

class Folder{  //Can be either system or folder
    private String name;
    private String type;
    private String path;
    private List<Folder> children; //To contain subFolder
    private List<String> file; //To contain list of files
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    public String getPath() {
        return path;
    }
    public void setPath(String path) {
        this.path = path;
    }
    public List<Folder> getChildren() {
        return children;
    }
    public void setChildren(List<Folder> children) {
        this.children = children;
    }
    public List<String> getFile() {
        return file;
    }
    public void setFile(List<String> file) {
        this.file = file;
    }
    @Override
    public String toString() {
        return "Folder [name=" + name + ", type=" + type + ", path=" + path + "\n, children=" + children + ", file="
                + file + "]";
    }
}

转换 key 然后解析为此类的代码

public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        String contents = new String(Files.readAllBytes(Paths.get("C:\\Users\\Sample.json"))); //Java 7 to read JSON into String from file

        Pattern pattern = Pattern.compile("\"children\":\\s*\\[\\s*[\"a-zA-Z\",\\s*]*]",Pattern.MULTILINE); //Pattren to find list of file i.e. content
        Matcher matcher = pattern.matcher(contents);
        while(matcher.find()) {
            String group = matcher.group();
            String newGroup = matcher.group().replaceAll("\"children\"", "\"file\"");
            contents = contents.replace(group, newGroup);
        }
        Folder folder = objectMapper.readValue(contents, Folder.class);
        System.out.println(folder);

    }

输出

Folder [name=rootf, type=system, path=Parsing/rootf
, children=[Folder [name=f1, type=folder, path=Parsing/rootf/f1
, children=[Folder [name=subf1, type=folder, path=Parsing/rootf/f1/subf1
, children=[Folder [name=text1.txt, type=file, path=Parsing/rootf/folder1/subf1/text1.txt
, children=null, file=[a, b, c]]], file=null], Folder [name=subf2, type=folder, path=Parsing/rootf/f1/subf2
, children=null, file=[]], Folder [name=text2.txt, type=file, path=TParsing/rootf/f1/text2.txt
, children=null, file=[d, e, f]]], file=null], Folder [name=text1.txt, type=file, path=Parsing/rootd/text1.txt
, children=null, file=[aa, bb]]], file=null]

现在你有了一个层次结构，即根目录下的系统，其中包含文件夹和文件。