使用 GSON 将 JSON 解析为 Java 对象

Question

我正在尝试将 json 文档从 jenkins API 映射到我自己的 java 对象。 json 文档如下所示：

{
    "assignedLabels": [
        {}
    ],
    "mode": "EXCLUSIVE",
    "nodeDescription": "Jenkins Master-Knoten",
    "nodeName": "",
    "numExecutors": 2,
    "description": null,
    "jobs": [
        {
            "name": "Job 1",
            "url": "https://build.example.com/jenkins/job/Job1/",
            "color": "disabled"
        },
        {
            "name": "Job 2",
            "url": "https://build.example.com/jenkins/job/Job2/",
            "color": "blue"
        }
    ],
    "overallLoad": {},
    "primaryView": {
        "name": "Alle",
        "url": "https://build.example.com/jenkins/"
    },
    "quietingDown": false,
    "slaveAgentPort": 0,
    "unlabeledLoad": {},
    "useCrumbs": false,
    "useSecurity": true,
    "views": [
        {
            "name": "Selection",
            "url": "https://build.example.com/jenkins/view/-All%Selection/"
        },
        {
            "name": "All",
            "url": "https://build.example.com/jenkins/"
        }
    ]
}

我的 java 模型如下所示：

public class JenkinsServer {
    private List<String> assignedLabels;
    private String url;

    private String mode;
    private String nodeName;
    private String nodeDescription;
    private String description;

    private boolean useSecurity;
    private boolean quietingDown;

    private JenkinsServerView primaryView;
    private List<JenkinsServerView> views;
    private List<JenkinsJob> jobs;

    // getters & setters
}

我现在做的就是打电话给

Gson gson = new Gson();
JenkinsServer server = gson.fromJson( reader, JenkinsServer.class );

但是我收到了这个异常

Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 6 column 5
    at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:374)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165)

我一直在互联网上搜索解决方案，但无法弄清楚我做错了什么。也许你们知道:-)

Answer 1

正如@Gimby 在评论中提到的，问题出在您的 json 数据中。

解决方案1：

因为 assignedLabels 是一个空值的字符串数组，一个选项是改变 json 没有大括号的数据，如下所示：

"assignedLabels": []

解决方案2：

将transient关键字添加到java class

中的变量

private transient List<String> assignedLabels;

解决方案3：

最后一个笨拙的实现方法是在 java class

中为要解析的所有变量添加 @Expose 注释

public class JenkinsServer {
    private List<String> assignedLabels;

    @Expose
    private String url;

    @Expose
    private String mode;

    @Expose
    private String nodeName;

    @Expose
    private String nodeDescription;

    @Expose
    private String description;

    @Expose
    private boolean useSecurity;

    @Expose
    private boolean quietingDown;

    @Expose
    private JenkinsServerView primaryView;

    @Expose
    private List<JenkinsServerView> views;

    @Expose
    private List<JenkinsJob> jobs;

    // getters & setters methods
}

然后添加解析逻辑以将您的 json 字符串解析为相应的 java 对象，如下所示：

Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();      
JenkinsServer server = gson.fromJson(reader, JenkinsServer.class);

使用 GSON 将 JSON 解析为 Java 对象

Parse JSON to Java Object using GSON

java

parsing

json

gson

jenkins