Google的JSON类库 Gson开发者指南(显示null值的json对象创建)

最新推荐文章于 2022-10-20 12:08:28 发布

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最新推荐文章于 2022-10-20 12:08:28 发布

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本文链接：https://blog.youkuaiyun.com/qingfengxia2013/article/details/82188906

本文展示了如何使用Gson库配置输出null值，并解释了在JSON序列化时使用null值的影响。通过实例演示了如何创建配置了输出null值的Gson实例，并提供了输出null值的具体代码实现。

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Null Object SupportThe default behaviour that is implemented in Gson is that null object fields are ignored. This allows for a more compact output format; however, the client must define a default value for these fields as the JSON format is converted back into its Java.

Here's how you would configure a Gson instance to output null: (显式的显示null值,需要创建一下的对象)
Gson gson = new GsonBuilder().serializeNulls().create();

NOTE: when serializing nulls with Gson, it will add a JsonNull element to the JsonElement structure. Therefore, this object can be used in custom serialization/deserialization.

Here's an example:

public class Foo {
private final String s;
private final int i;

public Foo() {
    this(null, 5);
}

public Foo(String s, int i) {
    this.s = s;
    this.i = i;
}
}

Gson gson = new GsonBuilder().serializeNulls().create();
Foo foo = new Foo();
String json = gson.toJson(foo);
System.out.println(json);

json = gson.toJson(null);
System.out.println(json);

======== OUTPUT ========
{"s":null,"i":5}
null