用Jackson将对象转储到String

Question

我正在使用Gson在我的应用程序中生成调试输出

Gson gson = new GsonBuilder().setPrettyPrinting().serializeNulls().create();
gson.toJson(myObject);

但在尝试序列化数据结构时,Gson确实抱怨循环引用错误.这可以用杰克逊图书馆完成吗？

UPD Gson 2.3.1:2014年11月20日发布

Added support to serialize objects with self-referential fields. The self-referential field is set to null in JSON. Previous version of Gson threw a StackOverflowException on encountering any self-referential fields.
    The most visible impact of this is that Gson can now serialize Throwable (Exception and Error)

Answer 1

要与杰森序列化:

public String serialize(Object obj, boolean pretty) {
    ObjectMapper mapper = new ObjectMapper();

    mapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);

    if (pretty) {
        return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
    }

    return mapper.writeValueAsString(obj);
}

Answer 2

杰克逊可以处理对象图中的循环:

1. @JsonIgnore,你完全省略了财产
2. @JsonManagedReference 和 @JsonBackReference
3. 扩展的自定义Serializer JsonSerializer

JsonSerializer当您仍希望提供有关该对象的某些信息但希望省略某些字段(导致该循环的字段)时,您将使用.例如:

import org.codehaus.jackson.map.JsonSerializer
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.SerializerProvider;

import java.io.IOException;

public class ParentReferenceSerializer extends JsonSerializer<Parent> {
    @Override
    public void serialize(Parent parent, JsonGenerator jgen,
        SerializerProvider provider)
            throws IOException, JsonProcessingException {
        jgen.writeStartObject();
        writeNumberField(jgen, "id", parent.getId());
        // ... other fields ...
        jgen.writeEndObject();
    }
}

然后在序列化的类中,您将使用@JsonSerialize注释:

@JsonSerialize(using = ParentReferenceSerializer.class)
public Parent getParent() {
    return parent;
}