Jackson之jackson-annotations
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原文链接:http://www.dubby.cn/detail.html?id=9071
字段命名
@JsonProperty
可以指定字段的命名(还可以指定这个字段需要参与序列化和反序列化)。@JsonProperty.value
:指定的字段名字@JsonProperty.index
:指定顺序,默写数据格式是基于顺序(JSON不是这种数据格式)@JsonProperty.defaultValue
:默认值。注意:这个属性目前为止并没有被core和data-bind使用;制备一些扩展模块使用。
字段包含
@JsonAutoDetect
:定义默认的字段包含规则@JsonIgnore
:忽略某个指定的字段:- 修饰字段,setter和getter中的任何一个,相当于所有都加了
- 除非使用
@JsonProperty
修饰,可以实现只忽略序列化或者反序列化
- 除非使用
- 修饰字段,setter和getter中的任何一个,相当于所有都加了
@JsonIgnoreProperties
:修饰类,指定忽略一个字段列表,或者忽略那些未知的字段@JsonIgnoreType
:修饰类,忽略指定的类型的字段@JsonInclude
:可以定义空值是否参与(反)序列化
字段文档,元数据
@JsonPropertyDescription
:2.3支持,给字段配置人类阅读的解释- core和data-bind不会使用这个注解,主要是被JSON Schema generator这个模块使用
反序列化和序列化的细节
@JsonFormat
:对于Date/Time字段,可以指定格式化格式@JsonUnwrapped
:指定某个字段(类型是POJO)序列化成扁平化,而不是嵌套对象,在反序列化时再包装成对象@JsonView
:可以定义视图
@JsonUnwrapped(prefix = "pre")
简单解释:
public class MyValue { public String name; JsonUnwrapped(prefix = "pre_", suffix = "_suf") public MyValue myValue; public int age; public Date date;}
序列化结果:
{"name":"杨正","pre_name_suf":null,"pre_age_suf":0,"pre_date_suf":null,"age":24,"date":"2017-12-09"}
@JsonView
简单解释:
public class JsonViewTest { public static void main(String[] args) throws IOException { ObjectMapper objectMapper = new ObjectMapper(); String json = "{\"username\":\"dubby.cn\",\"password\":\"123456\"}"; //反序列化,使用视图 User user = objectMapper.readerWithView(User.UserWithoutPassword.class).forType(User.class).readValue(json); System.out.println(user); user.password = "xxxx"; //序列化,使用视图 String result1 = objectMapper.writerWithView(User.UserWithoutPassword.class).writeValueAsString(user); System.out.println(result1); String result2 = objectMapper.writerWithView(User.UserWithPassword.class).writeValueAsString(user); System.out.println(result2); }}class User { @JsonView({UserWithoutPassword.class}) public String username; @JsonView({UserWithPassword.class}) public String password; public interface UserWithPassword extends UserWithoutPassword { } public interface UserWithoutPassword { } @Override public String toString() { return "User{" + "username='" + username + '\'' + ", password='" + password + '\'' + '}'; }}
反序列化细节
@JacksonInject
:指示某个字段的值是注入的,而不是从JSON中取出的@JsonAnySetter
:修饰一个2个参数的方法,任何JSON中有,而对象中没有的字段都会以(key,value)的形式传给这个方法@JsonCreator
:上篇文章自定义构造方法介绍过了@JsonSetter
:是@JsonProperty
的替代注解@JsonEnumDefaultValue
:反序列化时,如果遇到未定义的枚举值时,赋值为默认枚举
@JsonAnySetter
简单解释:
public class JsonAnySetterTest { public static void main(String[] args) throws IOException { String json = "{\"username\":\"dubby.cn\",\"password\":\"123456\",\"x-key\":\"xxx-value\",\"y-key\":\"yyy-value\"}"; ObjectMapper objectMapper = new ObjectMapper(); Data data = objectMapper.readValue(json, Data.class); System.out.println(data); }}class Data { public String username; public String password; public String other; @JsonAnySetter public void anySetter(String a, String b) { if (other == null) { other = ""; } other += a; other += ","; other += b; other += ";"; } @Override public String toString() { return "Data{" + "username='" + username + '\'' + ", password='" + password + '\'' + ", other='" + other + '\'' + '}'; }}
输出:
Data{username='dubby.cn', password='123456', other='x-key,xxx-value;y-key,yyy-value;'}
@JsonEnumDefaultValue
简单解释:
public class EnumTest { public static void main(String[] args) throws IOException { ObjectMapper objectMapper = new ObjectMapper(); objectMapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE, true); String json = "{\"myEnum\":\"V4\"}"; EnumData enumData = objectMapper.readValue(json, EnumData.class); System.out.println(enumData); }}class EnumData { public MyEnum myEnum; @Override public String toString() { return "EnumData{" + "myEnum=" + myEnum + '}'; }}enum MyEnum { V1, V2, V3, @JsonEnumDefaultValue Default;}
输出:
EnumData{myEnum=Default}
序列化细节
@JsonAnyGetter
:修饰一个方法,返回Map
,这个方法的返回值会被序列化成(key,value)形式@JsonGetter
:@JsonPropert
的替代注解@JsonPropertyOrder
:注定序列化的顺序@JsonRawValue
:被修饰的字段“准确”的显示出来,没有转义或装饰,双引号都不加@JsonValue
:指定序列化输出的值@JsonRootName
:使用这个指定的值作为JSON的根,前提是SerializationFeature.WRAP_ROOT_VALUE
已经打开了
@JsonAnyGetter
简单解释:
public class JsonAnyGetterTest { public static void main(String[] args) throws JsonProcessingException { ObjectMapper objectMapper = new ObjectMapper(); AnyGetterData data = new AnyGetterData(); data.data = "http://dubby.cn"; System.out.println(objectMapper.writeValueAsString(data)); }}class AnyGetterData { public String data; @JsonAnyGetter public Map other() { Map<String, String> map = new HashMap<>(); map.put("key1", "value1"); map.put("key2", "value2"); map.put("key3", "value3"); return map; }}
输出:
{"data":"http://dubby.cn","key1":"value1","key2":"value2","key3":"value3"}
@JsonPropertyOrder
简单解释:
public class JsonPropertyOrderTest { public static void main(String[] args) throws JsonProcessingException { ObjectMapper objectMapper = new ObjectMapper(); JsonPropertyOrderData data = new JsonPropertyOrderData(); data.name1 = "value1"; data.name2 = "value3"; data.name3 = "value4"; System.out.println(objectMapper.writeValueAsString(data)); }}@JsonPropertyOrder(value = {"name2", "name3", "name1"})class JsonPropertyOrderData { public String name1; public String name2; public String name3;}
输出:
{"name2":"value3","name3":"value4","name1":"value1"}
@JsonValue
简单解释:
public class JsonValueTest { public static void main(String[] args) throws IOException { ObjectMapper objectMapper = new ObjectMapper(); String json ="{\"name2\":\"value3\",\"name3\":\"value4\",\"name1\":\"value1\"}"; JsonValueData data = objectMapper.readValue(json, JsonValueData.class); System.out.println(data.toString()); System.out.println(objectMapper.writeValueAsString(data)); }}class JsonValueData { public String name1; public String name2; public String name3; @JsonValue public String other() { return name1+name2+name3; } @Override public String toString() { return "JsonValueData{" + "name1='" + name1 + '\'' + ", name2='" + name2 + '\'' + ", name3='" + name3 + '\'' + '}'; }}
输出:
JsonValueData{name1='value1', name2='value3', name3='value4'}"value1value3value4"
@JsonRootName
简单解释:
public class JsonRootNameTest { public static void main(String[] args) throws JsonProcessingException { ObjectMapper objectMapper = new ObjectMapper(); objectMapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true); RootData data = new RootData(); data.name1 = "value1"; data.name2 = "value2"; data.name3 = "value3"; System.out.println(objectMapper.writeValueAsString(data)); }}@JsonRootName(value = "root")class RootData { public String name1; public String name2; public String name3;}
输出:
{"root":{"name1":"value1","name2":"value2","name3":"value3"}}
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