JSON是这样的:

{
   "pageInfo": {
         "pageName": "abc",
         "pagePic": "http://example.com/content.jpg"
    }
}

Java类

class PageInfo {

    private String pageName;
    private String pagePic;

    // Getters and setters
}

将此JSON转换为Java类的代码。

    PageInfo pageInfo = JsonPath.parse(jsonString).read("$.pageInfo", PageInfo.class);

Maven

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.2.0</version>
</dependency>

The below example shows how to read the text in the question, represented as the "jsonText" variable. This solution uses the Java EE7 javax.json API (which is mentioned in some of the other answers). The reason I've added it as a separate answer is that the following code shows how to actually access some of the values shown in the question. An implementation of the javax.json API would be required to make this code run. The full package for each of the classes required was included as I didn't want to declare "import" statements.

javax.json.JsonReader jr = 
    javax.json.Json.createReader(new StringReader(jsonText));
javax.json.JsonObject jo = jr.readObject();

//Read the page info.
javax.json.JsonObject pageInfo = jo.getJsonObject("pageInfo");
System.out.println(pageInfo.getString("pageName"));

//Read the posts.
javax.json.JsonArray posts = jo.getJsonArray("posts");
//Read the first post.
javax.json.JsonObject post = posts.getJsonObject(0);
//Read the post_id field.
String postId = post.getString("post_id");

现在，在大家对这个答案投反对票之前因为它没有使用GSON, org。json, Jackson或任何其他可用的第三方框架，它是每个问题解析所提供文本的“所需代码”的示例。我很清楚JDK 9没有考虑遵守当前标准JSR 353，因此JSR 353规范应该与任何其他第三方JSON处理实现一样对待。

目前有许多开源库可以将JSON内容解析为对象，或者仅用于读取JSON值。您的要求只是读取值并将其解析为自定义对象。所以org。Json库在你的情况下是足够的。

使用org。解析它并创建JsonObject:

JSONObject jsonObj = new JSONObject(<jsonStr>);

现在，使用这个对象来获取你的值:

String id = jsonObj.getString("pageInfo");

你可以在这里看到一个完整的例子:

如何在Java中解析JSON

可以使用Apache @Model注释创建表示JSON文件结构的Java模型类，并使用它们访问JSON树中的各种元素。与其他解决方案不同，该解决方案完全没有反射，因此适用于不可能反射或开销很大的环境。

有一个示例Maven项目展示了这种用法。首先它定义了结构:

@Model(className="RepositoryInfo", properties = {
    @Property(name = "id", type = int.class),
    @Property(name = "name", type = String.class),
    @Property(name = "owner", type = Owner.class),
    @Property(name = "private", type = boolean.class),
})
final class RepositoryCntrl {
    @Model(className = "Owner", properties = {
        @Property(name = "login", type = String.class)
    })
    static final class OwnerCntrl {
    }
}

然后它使用生成的RepositoryInfo和Owner类来解析所提供的输入流，并在此过程中获取某些信息:

List<RepositoryInfo> repositories = new ArrayList<>();
try (InputStream is = initializeStream(args)) {
    Models.parse(CONTEXT, RepositoryInfo.class, is, repositories);
}

System.err.println("there is " + repositories.size() + " repositories");
repositories.stream().filter((repo) -> repo != null).forEach((repo) -> {
    System.err.println("repository " + repo.getName() + 
        " is owned by " + repo.getOwner().getLogin()
    );
})

就是这样!除此之外，这里还有一个生动的要点，展示了类似的例子以及异步网络通信。

本页的热门答案使用了太简单的例子，比如只有一个属性的对象(例如{name: value})。我认为这个简单但真实的例子可以帮助到一些人。

这是谷歌Translate API返回的JSON:

{
  "data": 
     {
        "translations": 
          [
            {
              "translatedText": "Arbeit"
             }
          ]
     }
}

我想检索“translatedText”属性的值。“Arbeit”使用谷歌的Gson。

两种可能的方法:

Retrieve just one needed attribute String json = callToTranslateApi("work", "de"); JsonObject jsonObject = new JsonParser().parse(json).getAsJsonObject(); return jsonObject.get("data").getAsJsonObject() .get("translations").getAsJsonArray() .get(0).getAsJsonObject() .get("translatedText").getAsString(); Create Java object from JSON class ApiResponse { Data data; class Data { Translation[] translations; class Translation { String translatedText; } } } ... Gson g = new Gson(); String json =callToTranslateApi("work", "de"); ApiResponse response = g.fromJson(json, ApiResponse.class); return response.data.translations[0].translatedText;

JSON是这样的:

{
   "pageInfo": {
         "pageName": "abc",
         "pagePic": "http://example.com/content.jpg"
    }
}

Java类

class PageInfo {

    private String pageName;
    private String pagePic;

    // Getters and setters
}

将此JSON转换为Java类的代码。

    PageInfo pageInfo = JsonPath.parse(jsonString).read("$.pageInfo", PageInfo.class);

Maven

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.2.0</version>
</dependency>