java - 使用Gson创建对象数组

Question

我想将此 JSON 字符串转换为可以在 Java 中操作的对象数组。

String jsonExample = "" +
            "{"c":[{"v":"03/10/2013"},{"v":23},{"v":112}]},"+
            "{"c":[{"v":"04/10/2013"},{"v":14},{"v":232}]},"+
            "{"c":[{"v":"05/10/2013"},{"v":18},{"v":145}]},"+
            "{"c":[{"v":"06/10/2013"},{"v":22},{"v":211}]},"+
            "{"c":[{"v":"07/10/2013"},{"v":18},{"v":198}]},"+
            "{"c":[{"v":"08/10/2013"},{"v":15},{"v":215}]}";

首先，我取消转义:

String unescape = StringEscapeUtils.unescapeHtml4(jsonExample2);

然后，我尝试使用Gson，

Gson gson = new Gson();
ViewsHistoric viewHistoric = gson.fromJson(unescape, ViewsHistoric.class);

具有以下类:

    public static class ViewsHistoric {
    private List<Row> r;
    public List<Row> getR() {return r;}
    public ViewsHistoric() {}
}

public static class Row {
    private Triplet c;
    public Triplet getC() {return c;}
    public Row() {}
}

public static class Triplet {
    private String v;

    public String getV() {return v; }
    public Triplet() {}
}

但是我收到错误:

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 2

实际上，在过去的几个小时内，我已经尝试了许多其他的 Gson 类组合，但没有成功。

谁能告诉我如何将 json 字符串转换为 java 对象？

Answer 1

有两件事:

1. 您的 JSON 格式无效(即使在取消转义之后也是如此)。
2. 您的 Triplet 类是一个对象，而不是 JSON 数组。

为了使其正常工作，我对您的代码进行了一些修改。这里有一个工作示例

public class Q24000071 {

    public static void main(String[] args) {
             //the 'r' attribute, corresponding to 'ViewsHistoric' class, was missing
        String jsonExample = "{\"r\": ["
                + "{"c":[{"v":"03/10/2013"},{"v":23},{"v":112}]},"
                + "{"c":[{"v":"04/10/2013"},{"v":14},{"v":232}]},"
                + "{"c":[{"v":"05/10/2013"},{"v":18},{"v":145}]},"
                + "{"c":[{"v":"06/10/2013"},{"v":22},{"v":211}]},"
                + "{"c":[{"v":"07/10/2013"},{"v":18},{"v":198}]},"
                + "{"c":[{"v":"08/10/2013"},{"v":15},{"v":215}]}"
                + "]}";

        String unescape = StringEscapeUtils.unescapeHtml4(jsonExample);
        System.out.println(unescape);

        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        ViewsHistoric viewHistoric = gson.fromJson(unescape,
                ViewsHistoric.class);
        System.out.println(gson.toJson(viewHistoric));
    }

    public static class ViewsHistoric {

        private List<Row> r;

        public List<Row> getR() {
            return r;
        }

        public ViewsHistoric() {
        }
    }

    public static class Row {

        // Triplet is an array in the original JSON
            // of three elements, but an array.
        private Triplet[] c;

        public Triplet[] getC() {
            return c;
        }

        public Row() {
        }
    }

    public static class Triplet {

        private String v;

        public String getV() {
            return v;
        }

        public Triplet() {
        }
    }
}