如何使用 GSON 解析与 JSON 数组混合的复杂 JSON 字符串？

Question

下面是我的 JSON 字符串，我正在尝试使用 GSON 解析这个 JSON 字符串，因为我发现它很容易使用。

{
"HasChanged":true,
"Version":1,
"LastModifiedDate":1390561121310,
    "DATACENTERS":
        [
            {
            "Name": "DC1",
            "TotalNumberOfServers":4,
            "PrimaryData":[{"0":"1", "1":"2", "2":"3", "3":"4"}],
            "SecondaryData":[{"0":"2", "1":"3", "2":"4", "3":"1"}],
            "MachineMapping":[{"3":"dc11115.dc1.domain.com"}, {"2":"dc11114.dc1.domain.com"}, {"1":"dc11113.dc1.domain.com"}, {"4":"dc11116.dc1.domain.com"}]
            },
            {
            "Name": "DC2",
            "TotalNumberOfServers":4,
            "PrimaryData":[{"1":"1", "5":"2", "2":"3", "6":"4"}],
            "SecondaryData":[{"7":"1", "0":"8", "2":"5", "10":"9"}],
            "MachineMapping":[{"3":"dc21147.dc2.domain.com"}, {"2":"dc21146.dc2.domain.com"}, {"1":"dc21145.dc2.domain.com"}, {"4":"dc21148.dc2.domain.com"}]
            }
        ]
}

解析完上面的JSON String之后，我需要将每一个DataCenter的数据存储在下面的数据结构中——

Map<String, Map<String, String>> primaryData
Map<String, Map<String, String>> secondaryData
Map<String, Map<String, String>> machineMapping

对于 JSON 字符串中的PrimaryData 标记-

Here Key of `primaryData` map is `DC1` and value is {"0":"1", "1":"2", "2":"3", "3":"4"} which is for `PrimaryData` tag.
Similarly, another Key of `primaryData` map is `DC2` and value is {"1":"1", "5":"2", "2":"3", "6":"4"} which is for `PrimaryData` tag.

对于 JSON 字符串中的 SecondaryData 标记也是如此 -

Here Key of `secondaryData` map is `DC1` and value is {"0":"2", "1":"3", "2":"4", "3":"1"} which is for `SecondaryData` tag.
Similarly, another Key of `secondaryData` map is `DC2` and value is {"7":"1", "0":"8", "2":"5", "10":"9"} which is for `SecondaryData` tag.

对于 JSON 字符串中的 MachineMapping 标记也是如此 -

Here Key of `machineMapping` is `DC1` and value is {"3":"dc11115.dc1.domain.com"}, {"2":"dc11114.dc1.domain.com"}, {"1":"dc11113.dc1.domain.com"}, {"4":"dc11116.dc1.domain.com"} which is for MachineMapping tag.
Similarly another key of `machineMapping` is `DC2` and value is {"3":"dc21147.dc2.domain.com"}, {"2":"dc21146.dc2.domain.com"}, {"1":"dc21145.dc2.domain.com"}, {"4":"dc21148.dc2.domain.com"} which is for `MachineMapping` tag.

这是我第一次处理这个复杂的 JSON 字符串的解析，所以我开始使用 GSON，因为我发现它很容易使用。这是我迄今为止尝试过的，我能够提取大部分字段，但不知道如何将PrimaryData 对象映射到Map，然后为其他人做同样的事情？

private static Map<String, Map<String, String>> primaryData = new LinkedHashMap<String, Map<String, String>>();
private static Map<String, Map<String, String>> secondaryData = new LinkedHashMap<String, Map<String, String>>();
private static Map<String, Map<String, String>> machineMappedData = new LinkedHashMap<String, Map<String, String>>();

public static void main(String[] args) {

    String jsonLine = "my json string";

    JsonElement jelement = new JsonParser().parse(jsonLine);
    JsonObject jobject = jelement.getAsJsonObject();

    boolean changed = jobject.get("HasChanged").getAsBoolean();
    String timestamp = jobject.get("LastModifiedDate").getAsString();
    String version = jobject.get("Version").getAsString();

    System.out.println(changed);
    System.out.println(timestamp);
    System.out.println(version);

    if (changed) {
        JsonArray jarray = jobject.getAsJsonArray("DATACENTERS");
        for (int i = 0; i < jarray.size(); i++) {
            Map<String, String> data = new LinkedHashMap<String, String>();

            jobject = jarray.get(i).getAsJsonObject();
            String dcName = jobject.get("Name").getAsString();
            int servers = jobject.get("TotalNumberOfServers").getAsInt();
            System.out.println(dcName);
            System.out.println(servers);

            if (servers > 0) {
                JsonArray jarray1 = jobject.getAsJsonArray("PrimaryData");
                System.out.println(jarray1);
                for (int j = 0; j < jarray1.size(); j++) {
                    jobject = jarray1.get(j).getAsJsonObject();
                    System.out.println(jobject);

                    // not sure how to map the PrimaryData object to a Map here?

                }
            }
        }
    }
}

但是我被卡住了，不知道如何在这里将 JSON 对象放入 Map 中？谁能帮我解决这个问题？

Answer 1

您应该做的是定义您的 JSON 映射到的 Java 类：

public class MyJsonResponse
{
    private boolean HasChanged;
    private int Version;
    private long LastModifiedDate;
    private List<DataCenter> DATACENTERS;

    // Getters/Setters for above
}

public class DataCenter
{
    private String Name;
    private int TotalNumberOfServers;
    private List<Map<String,String>> PrimaryData;
    private List<Map<String,String>> SecondaryData;
    private List<Map<String,String>> MachineMapping; 

    // getters and setters for all of the above
}

定义了这些类后，就很简单了：

MyJsonResponse response = new Gson().fromJson(jsonString, MyJsonResponse.class);

另外值得注意的是，由于 JSON 变量名不符合 Java 命名约定，您应该还通过@SerializedName 注解对其进行转换。

@SerializedName("DATACENTERS")
private List<DataCenter> dataCenters;

例如。