使用 Gson 将 Java 对象转换为 JsonObject
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Using Gson convert Java object into JsonObject
提问by user304582
I have a Java object, and I want to output it as a JSON string. BUT I want to avoid printing out a property in the Java object. I know that I could do this using GsonBuilder's excludeFieldsWithoutExposeAnnotation() method. However, I thought I'd try the alternate approach of removing the property from the JsonObject before printing it out. The following code works:
我有一个 Java 对象，我想将它输出为 JSON 字符串。但我想避免打印出 Java 对象中的属性。我知道我可以使用 GsonBuilder 的 excludeFieldsWithoutExposeAnnotation() 方法来做到这一点。但是，我想我会尝试在打印之前从 JsonObject 中删除属性的替代方法。以下代码有效：
Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd' 'HH:mm:ss").create();
String javaObjectString = gson.toJson(javaObject);
//javaObjectString currently include "property":"value"
JsonElement jsonElement = gson.toJsonTree(javaObjectString, javaObject.getClass());
JsonObject jsonObject = (JsonObject) jsonElement;
jsonObject.remove("property");
javaObjectString = gson.toJson(jsonObject);
//javaObjectString currently no longer includes "property":"value"
However, it feels a but hacky because I have to output the Java object to a String, and then create a JsonElement from the String, and then cast the JsonElement to a JsonObject.
但是，感觉有点hacky，因为我必须将Java对象输出到String，然后从String创建一个JsonElement，然后将JsonElement转换为JsonObject。
Is there a more direct way to go from a Java object to a JsonObject?
有没有更直接的方法可以从 Java 对象转到 JsonObject？
回答by Sotirios Delimanolis
You don't need the intermediary String. Serialize your Java object to a JsonElementdirectly with Gson#toJsonTree(Object). Cast that value to whatever type you expect (JSON object, array, or primitive), perform your removal and invoke its toString()method to retrieve its JSON representation as a String.
你不需要中介String。将您的 Java 对象JsonElement直接序列化为Gson#toJsonTree(Object). 将该值转换为您期望的任何类型（JSON 对象、数组或原语），执行删除并调用其toString()方法以将其 JSON 表示检索为String.
For example,
例如，
Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd' 'HH:mm:ss").create();
// JSON data structure
JsonElement jsonElement = gson.toJsonTree(javaObject);
JsonObject jsonObject = (JsonObject) jsonElement;
// property removal
jsonObject.remove("property");
// serialization to String
String javaObjectString = jsonObject.toString();
You can always use the Gson#toJsonoverload that accepts a JsonElementto serialize it directly to a stream if you want to skip that last Stringobject creation.
如果您想跳过最后一个对象的创建，您始终可以使用Gson#toJson接受 a的重载JsonElement将其直接序列化为流String。
