使用jackson转换Java对象时如何忽略可选属性

Question

我正在使用Jackson 1.9.2(org.codehaus.jackson)来修改从Java对象到匹配的JSON构造.这是我的java对象:

Class ColorLight {
    String type;
    boolean isOn;
    String value;

    public String getType(){
        return type;
    }

    public setType(String type) {
        this.type = type;
    }

    public boolean getIsOn(){
        return isOn;
    }

    public setIsOn(boolean isOn) {
        this.isOn = isOn;
    }

    public String getValue(){
        return value;
    }

    public setValue(String value) {
        this.value = value;
    }
}

如果我做了以下转换,我会得到我想要的结果.

ColorLight light = new ColorLight();
light.setType("red");
light.setIsOn("true");
light.setValue("255");
objectMapper mapper = new ObjectMapper();
jsonString = mapper.writeValueAsString();

jsonString会是这样的:

{"type":"red","isOn":"true", "value":"255"}

但有时我没有isOn属性的值

ColorLight light = new ColorLight();
light.setType("red");
light.setValue("255");

但是jsonString仍然像:

{"type":"red","isOn":"false", "value":"255"}

其中"isOn:false"是Java布尔类型的默认值,我不希望它在那里.如何删除最终json构造中的isOn属性？

{"type":"red","value":"255"}

Answer 1

要跳过该值,如果它不存在:

• 使用Boolean而不是boolean原语(boolean值始终设置为true或false).
• 配置Jackson不使用@JsonInclude(Include.NON_NULL)或序列化空值@JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL),具体取决于版本.

Answer 2

您可以使用@JsonSerialize(include = JsonSerialize.Inclusion.NON_DEFAULT)1.x注释标记您的类,该注释指示仅包含具有与默认设置不同的值的属性(意味着当Bean使用其无参数构造函数构造时具有的值).

该@JsonInclude(JsonInclude.Include.NON_DEFAULT)注释用于版本2.x的

这是一个例子:

public class JacksonInclusion {

    @JsonSerialize(include = JsonSerialize.Inclusion.NON_DEFAULT)
    public static class ColorLight {
        public String type;
        public boolean isOn;

        public ColorLight() {
        }

        public ColorLight(String type, boolean isOn) {
            this.type = type;
            this.isOn = isOn;
        }
    }

    public static void main(String[] args) throws IOException {
        ColorLight light = new ColorLight("value", false);
        ObjectMapper mapper = new ObjectMapper();
        System.out.println(mapper.writeValueAsString(light));
    }
}

输出:

{"type":"value"}