java 使用 gson 解析 JSON 数组
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Parsing JSON array with gson
提问by user1047833
I am having trouble parsing my JSON which i get from javascript. The format of JSON is this:
我在解析我从 javascript 获得的 JSON 时遇到问题。JSON 的格式是这样的：
[{"positions":[{"x":50,"y":50},{"x":82,"y":50},{"x":114,"y":50},{"x":146,"y":50}]},{"positions":[{"x":210,"y":50},{"x":242,"y":50},{"x":274,"y":50}]}]
So far i have been able to get this far:
到目前为止，我已经能够做到这一点：
{"positions":[{"x":50,"y":50},{"x":82,"y":50},{"x":114,"y":50},{"x":146,"y":50}]}
But i also need to now create a class with those positions. I havnt been working on the class, since i tried printing out the output first, but i am unable to break it down further. I am getting this error message:
但我现在还需要用这些职位创建一个类。我没有在这门课上工作，因为我先尝试打印输出，但我无法进一步分解它。我收到此错误消息：
java.lang.IllegalStateException: This is not a JSON Array.
java.lang.IllegalStateException：这不是 JSON 数组。
And my code is this:
我的代码是这样的：
JsonParser parser = new JsonParser();
String ships = request.getParameter("JSONships");
JsonArray array = parser.parse(ships).getAsJsonArray();
System.out.println(array.get(0).toString());
JsonArray array2 = parser.parse(array.get(0).toString()).getAsJsonArray();
System.out.println(array2.get(0).toString());
I have also tried to do it this way:
我也尝试过这样做：
Gson gson = new Gson() ;
String lol = (gson.fromJson(array.get(0), String.class));
System.out.println(lol);
In which case i get:
在这种情况下，我得到：
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected STRING but was BEGIN_OBJECT
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: 预期为 STRING 但为 BEGIN_OBJECT
In the end, i want to loop through positions, creating class for each "positions", which contains a List with another class Position, which has the int x, y.
最后，我想遍历位置，为每个“位置”创建类，其中包含一个带有另一个类 Position 的 List，它具有 int x, y。
Thank you for your time.
感谢您的时间。
回答by Boris Strandjev
Define your classes and you will get everything you need using gson:
定义您的类，您将使用 gson 获得所需的一切：
public class Class1 {
private int x;
private List<Class2> elements;
}
And the inner class:
和内部类：
public class Class2 {
private String str1;
private Integer int2;
}
Now you can parse a json string of the outer class just like that:
现在你可以像这样解析外部类的 json 字符串：
gson.fromJson(jsonString, Class1.class);
Your error while using Gson is that you try to parse a complex object in String, which is not possible.
您在使用 Gson 时的错误是您尝试解析 中的复杂对象String，这是不可能的。
