Java Jackson ObjectMapper DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT
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Hymanson ObjectMapper DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT
提问by user2957698
I am using Hymanson for JSON serialization/deserialization in my Jersey application. I want to read the empty strings in JSON to null value in my java POJO property. I tried to set the DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT on Object Mapper but it is not working. Here is the code below
我在 Jersey 应用程序中使用 Hymanson 进行 JSON 序列化/反序列化。我想在我的 java POJO 属性中将 JSON 中的空字符串读取为空值。我试图在对象映射器上设置 DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT 但它不起作用。这是下面的代码
import java.io.IOException;
import org.codehaus.Hymanson.JsonParseException;
import org.codehaus.Hymanson.map.DeserializationConfig;
import org.codehaus.Hymanson.map.JsonMappingException;
import org.codehaus.Hymanson.map.ObjectMapper;
public class TestMapper {
/**
* @param args
*/
public static void main(String[] args) {
TestMapper.testJson();
}
public static void testJson(){
String jsonString = "{\"name\":\"First Name\",\"phone\":\"\",\"unknown\":\"test\"}";
ObjectMapper result = new ObjectMapper();
//result.setDeserializationConfig(result.getDeserializationConfig().with(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT));
//result.enable(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
/*DeserializationConfig deserializeConfig = result.getDeserializationConfig();
deserializeConfig.with(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);*/
result.configure(DeserializationConfig.Feature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true);
result.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
try {
TestBean testBean = result.readValue(jsonString, TestBean.class);
if(testBean.getPhone()!=null&& testBean.getPhone().equals("")){
System.out.print("Phone Number is empty string");
}else{
System.out.print("Phone Number is null");
}
} catch (JsonParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (JsonMappingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
The bean is as below
豆子如下
public class TestBean {
private String name;
private String phone;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public TestBean(String name, String phone) {
super();
this.name = name;
this.phone = phone;
}
public TestBean() {
super();
}
}
The output is always
输出总是
Phone Number is empty string
I am not sure why is this not working. I am using Hymanson 1.9.2.
我不确定为什么这不起作用。我正在使用Hyman逊 1.9.2。
回答by Sotirios Delimanolis
Note the javadoc of ACCEPT_EMPTY_STRING_AS_NULL_OBJECT
注意javadoc ACCEPT_EMPTY_STRING_AS_NULL_OBJECT
Feature that can be enabled to allow JSON empty String value ("") to be bound to POJOs as null.
可以启用以允许 JSON 空字符串值 ("") 绑定到 POJO 为 null 的功能。
So an empty Stringcan be used to map nullto a POJO. A Stringis not a POJO, it is considered a JSON primitive value.
所以String可以使用空来映射null到 POJO。AString不是 POJO，它被认为是 JSON 原始值。
You cannot use that here.
你不能在这里使用它。
ACCEPT_EMPTY_STRING_AS_NULL_OBJECTwould work for something like
ACCEPT_EMPTY_STRING_AS_NULL_OBJECT会为类似的东西工作
{"name":"First Name","phone":"","unknown":"test"}
Where you would make the TestBean.phonefield of some POJO type like
您可以在哪里制作TestBean.phone某些 POJO 类型的字段，例如
class Phone {
private String number;
}
Then deserializing would make the phonefield be null.
然后反序列化将使该phone字段成为null.
