目录
A Public Field
有get，set方法时，则序列化，反序列化都支持
@Data
@AllArgsConstructor
@NoArgsConstructor
public class MyDtoAccessLevel {
private String stringValue;
int intValue;
protected float floatValue;
public boolean booleanValue;
}
ObjectMapper mapper = new ObjectMapper();
MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
String jsonAsString = "{\"stringValue\":\"dtoString\"}";
MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
System.out.println(dtoObject1);
执行结果
{
"stringValue":null,"intValue":0,"floatValue":0.0,"booleanValue":false}
MyDtoAccessLevel(stringValue=dtoString, intValue=0, floatValue=0.0, booleanValue=false)
无get，set方法时，则序列化，反序列化仅支持public
public class MyDtoAccessLevel {
private String stringValue;
int intValue;
protected float floatValue;
public boolean booleanValue;
@Override
public String toString() {
return "MyDtoAccessLevel{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + ", floatValue=" + floatValue + ", booleanValue=" + booleanValue + '}';
}
}
ObjectMapper mapper = new ObjectMapper();
MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
String jsonAsString = "{\"booleanValue\":false}";
MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
System.out.println(dtoObject1);
结果
{
"booleanValue":false}
MyDtoAccessLevel{
stringValue='null', intValue=0, floatValue=0.0, booleanValue=false}
反序列化仅支持public字段，如果JSON串包含其他字段否则无法识别，从而报错
String jsonAsString = "{\"booleanValue\":false,\"stringValue\":\"dtoString\"}";
MyDtoAccessLevel dtoObject1 = mapper.readValue(jsonAsString, MyDtoAccessLevel.class);
System.out.println(dtoObject1);
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "stringValue" (class javabasic.enumprac.MyDtoAccessLevel), not marked as ignorable (one known property: "booleanValue"])
at [Source: (String)"{"booleanValue":false,"stringValue":"dtoString"}"; line: 1, column: 38] (through reference chain: javabasic.enumprac.MyDtoAccessLevel["stringValue"])
A Getter Makes a Non-Public Field Serializable and Deserializable
public class MyDtoWithGetter {
private String stringValue;
private int intValue;
public String getStringValue() {
return stringValue;
}
@Override
public String toString() {
return "MyDtoWithGetter{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + '}';
}
}
有get方法的Non-Public Field支持序列化和反序列化
ObjectMapper mapper = new ObjectMapper();
MyDtoWithGetter dtoObject = new MyDtoWithGetter();
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
String jsonAsString = "{\"stringValue\":\"dtoString\"}";
MyDtoWithGetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithGetter.class);
System.out.println(dtoObject1);
结果
{
"stringValue":null}
MyDtoWithGetter{
stringValue='dtoString', intValue=0}
Json串反序列化时，仅支持有get方法的Non-Public Field，否则无法解析报错
String jsonAsString = "{\"intValue\":11,\"stringValue\":\"dtoString\"}";
MyDtoWithGetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithGetter.class);
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "intValue" (class javabasic.enumprac.MyDtoWithGetter), not marked as ignorable (one known property: "stringValue"])
at [Source: (String)"{"intValue":11,"stringValue":"dtoString"}"; line: 1, column: 15] (through reference chain: javabasic.enumprac.MyDtoWithGetter["intValue"])
A Setter Makes a Non-Public Field Deserializable Only
public class MyDtoWithSetter {
private String stringValue;
private int intValue;
public void setIntValue(int intValue) {
this.intValue = intValue;
}
@Override
public String toString() {
return "MyDtoWithSetter{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + '}';
}
}
the setter should only make the field deserializable, but not serializable:
ObjectMapper mapper = new ObjectMapper();
MyDtoWithSetter dtoObject = new MyDtoWithSetter ();
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class javabasic.enumprac.MyDtoWithSetter and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
只能解析有set方法属性，否则报错
ObjectMapper mapper = new ObjectMapper();
String jsonAsString = "{\"intValue\":1}";
MyDtoWithSetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithSetter.class);
System.out.println(dtoObject1);
MyDtoWithSetter{
stringValue='null', intValue=1}
ObjectMapper mapper = new ObjectMapper();
String jsonAsString = "{\"stringValue\":\"dtoString\",\"intValue\":\"22\"}";
MyDtoWithSetter dtoObject1 = mapper.readValue(jsonAsString, MyDtoWithSetter.class);
System.out.println(dtoObject1);
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "stringValue" (class javabasic.enumprac.MyDtoWithSetter), not marked as ignorable (one known property: "intValue"])
at [Source: (String)"{"stringValue":"dtoString","intValue":"22"}"; line: 1, column: 17] (through reference chain: javabasic.enumprac.MyDtoWithSetter["stringValue"])
Make All Fields Globally Serializable
public class MyDtoAccessLevel {
private String stringValue;
int intValue;
protected float floatValue;
public boolean booleanValue;
@Override
public String toString() {
return "MyDtoAccessLevel{" + "stringValue='" + stringValue + '\'' + ", intValue=" + intValue + ", floatValue=" + floatValue + ", booleanValue=" + booleanValue + '}';
}
}
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
MyDtoAccessLevel dtoObject = new MyDtoAccessLevel();
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
{
"stringValue":null,"intValue":0,"floatValue":0.0,"booleanValue":false}
Change the Name of a Property on Serialization/Deserialization
针对相同的输出代码
ObjectMapper mapper = new ObjectMapper();
MyDto dtoObject = new MyDto();
dtoObject.setStringValue("a");
String dtoAsString = mapper.writeValueAsString(dtoObject);
System.out.println(dtoAsString);
public class MyDto {
private String stringValue;
public MyDto() {
super();
}
public String getStringValue() {
return stringValue;
}
public void setStringValue(String stringValue) {
this.stringValue = stringValue;
}
}
结果
{
"stringValue":"a"}
public class MyDto {
private String stringValue;
public MyDto() {
super();
}
@JsonProperty("strVal")
public String getStringValue() {
return stringValue;
}
public void setStringValue(String stringValue) {
this.stringValue = stringValue;
}
}
结果
{
"strVal":"a"}
Ignore a Field on Serialization or Deserialization
Further reading: Jackson Ignore Properties on Marshalling
通过在getter上添加@JsonIgnore注释禁止该字段的序列化，通过在setter上应用@JsonProperty注释来启用该字段的反序列化
public class User {
public String name;
private String password;
@JsonIgnore
public String getPassword() {
return password;
}
@JsonProperty
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" + "name='" + name + '\'' + ", password='" + password + '\'' + '}';
}
}
ObjectMapper mapper = new ObjectMapper();
User userObject = new User();
userObject.setPassword("thePassword");
userObject.setPassword("mingming");
String userAsString = mapper.writeValueAsString(userObject);
System.out.println(userAsString);
String jsonAsString = "{\"name\":\"mingming\",\"password\":\"thePassword\"}";
User userObject1 = mapper.readValue(jsonAsString, User.class);
System.out.println(userObject1);
结果：
{
"name":null}
User{
name='mingming', password='thePassword'}
-----------------------------------------------------------------------------读书笔记摘自 文章：Jackson – Decide What Fields Get Serialized/Deserialized