使对象映射器writeValueAsString方法包含空值

Question

private ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(object);

object = {"name": "John", "id": 10}
json   = {"name": "John", "id": 10}

object = {"name": "John", "id": null}
json   = {"name": "John"}

Answer 1

默认情况下，Jackson应该将null字段序列化为null。请参阅以下示例

public class Example {

    public static void main(String... args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
        String json = mapper.writeValueAsString(new Test());
        System.out.println(json);
    }

    static class Test {
        private String help = "something";
        private String nope = null;

        public String getHelp() {
            return help;
        }

        public void setHelp(String help) {
            this.help = help;
        }

        public String getNope() {
            return nope;
        }

        public void setNope(String nope) {
            this.nope = nope;
        }
    }
}

印刷品

{
  "help" : "something",
  "nope" : null
}

你不需要做什么特别的事。