傑克遜1.9.x的使用自定義的註解解串

Question

我有一個註釋，以表明JSON屬性名

public @interface ApiField { 

     /**json property name*/ 
     public String value() default ""; 

    } 

而且這樣

public class User{ 
    @ApiField("last_name") 
    String lastName; 
    public String getLastName(){...} 

    public void setLastName(String lastName){...} 
} 

一類和JSON字符串

{"last_name":"bob"} 

如何使用此註解來指示屬性名稱i而不是 @JsonProperty？

Answer 1

可以使用AnnotationIntrospector實現這一

ApiAnnotationIntrospector

import java.lang.annotation.Annotation; 

import org.codehaus.jackson.Version; 
import org.codehaus.jackson.Versioned; 
import org.codehaus.jackson.map.AnnotationIntrospector; 
import org.codehaus.jackson.map.JsonDeserializer; 
import org.codehaus.jackson.map.KeyDeserializer; 
import org.codehaus.jackson.map.annotate.JsonSerialize.Typing; 
import org.codehaus.jackson.map.introspect.Annotated; 
import org.codehaus.jackson.map.introspect.AnnotatedClass; 
import org.codehaus.jackson.map.introspect.AnnotatedConstructor; 
import org.codehaus.jackson.map.introspect.AnnotatedField; 
import org.codehaus.jackson.map.introspect.AnnotatedMethod; 
import org.codehaus.jackson.map.introspect.AnnotatedParameter; 
import org.codehaus.jackson.type.JavaType; 
import org.codehaus.jackson.util.VersionUtil; 

public class ApiAnnotationIntrospector extends AnnotationIntrospector implements 
     Versioned { 

    @Override 
    public Version version() { 
     return VersionUtil.versionFor(getClass()); 
    } 

    @Override 
    public boolean isHandled(Annotation ann) { 
     Class<?> cls = ann.annotationType(); 
     if (ApiField.class == cls) { 
      return true; 
     } 
     return false; 
    } 

    @Override 
    public String findRootName(AnnotatedClass ac) { 
     return null; 
    } 

    @Override 
    public String[] findPropertiesToIgnore(AnnotatedClass ac) { 
     return null; 
    } 

    @Override 
    public Boolean findIgnoreUnknownProperties(AnnotatedClass ac) { 
     return null; 
    } 

    @Override 
    public boolean isIgnorableMethod(AnnotatedMethod m) { 
     return false; 
    } 

    @Override 
    public boolean isIgnorableConstructor(AnnotatedConstructor c) { 
     return false; 
    } 

    @Override 
    public boolean isIgnorableField(AnnotatedField f) { 
     return false; 
    } 

    @Override 
    public Object findSerializer(Annotated am) { 
     return null; 
    } 

    @Override 
    public Class<?> findSerializationType(Annotated a) { 
     return null; 
    } 

    @Override 
    public Typing findSerializationTyping(Annotated a) { 
     return null; 
    } 

    @Override 
    public Class<?>[] findSerializationViews(Annotated a) { 
     return null; 
    } 

    @Override 
    public String[] findSerializationPropertyOrder(AnnotatedClass ac) { 
     return null; 
    } 

    @Override 
    public Boolean findSerializationSortAlphabetically(AnnotatedClass ac) { 
     return null; 
    } 

    @Override 
    public String findGettablePropertyName(AnnotatedMethod am) { 
     return null; 
    } 

    @Override 
    public boolean hasAsValueAnnotation(AnnotatedMethod am) { 
     return false; 
    } 

    @Override 
    public String findEnumValue(Enum<?> value) { 
     return null; 
    } 

    @Override 
    public String findSerializablePropertyName(AnnotatedField af) { 
     return getPropertyName(af); 
    } 

    @Override 
    public Object findDeserializer(Annotated am) { 
     return null; 
    } 

    @Override 
    public Class<? extends KeyDeserializer> findKeyDeserializer(Annotated am) { 
     return null; 
    } 

    @Override 
    public Class<? extends JsonDeserializer<?>> findContentDeserializer(
      Annotated am) { 
     return null; 
    } 

    @Override 
    public Class<?> findDeserializationType(Annotated am, JavaType baseType, 
      String propName) { 
     return null; 
    } 

    @Override 
    public Class<?> findDeserializationKeyType(Annotated am, 
      JavaType baseKeyType, String propName) { 
     return null; 
    } 

    @Override 
    public Class<?> findDeserializationContentType(Annotated am, 
      JavaType baseContentType, String propName) { 
     return null; 
    } 

    @Override 
    public String findSettablePropertyName(AnnotatedMethod am) { 
     return null; 
    } 

    @Override 
    public String findDeserializablePropertyName(AnnotatedField af) { 
     return getPropertyName(af); 
    } 

    @Override 
    public String findPropertyNameForParam(AnnotatedParameter param) { 
     return null; 
    } 

    private String getPropertyName(AnnotatedField af) { 
     ApiField annotation = af.getAnnotation(ApiField.class); 
     if (annotation != null && annotation.value() != "") { 
      return annotation.value(); 
     } 
     return null; 
    } 

} 

然後改變你的ObjectMapper如下

ObjectMapper mapper = new ObjectMapper(); 

AnnotationIntrospector primary = new ApiAnnotationIntrospector(); 
AnnotationIntrospector secondary = new JaxbAnnotationIntrospector(); 
AnnotationIntrospector pair = new AnnotationIntrospector.Pair(primary, 
     secondary); 

mapper.getDeserializationConfig().setAnnotationIntrospector(pair); 
mapper.getSerializationConfig().setAnnotationIntrospector(pair); 

我的測試

public static class Type { 
    private String code; 

    private String description; 

    @ApiField("raw-value") 
    private String value; 

    public Type() { 
    } 

    public Type(String code, String description, String value) { 
     super(); 
     this.code = code; 
     this.description = description; 
     this.value = value; 
    } 

    public String getCode() { 
     return code; 
    } 

    public void setCode(String code) { 
     this.code = code; 
    } 

    public String getDescription() { 
     return description; 
    } 

    public void setDescription(String description) { 
     this.description = description; 
    } 

    public String getValue() { 
     return value; 
    } 

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

} 

和測試用例

Type t = new Type("c", "d", "e"); 
StringWriter sw = new StringWriter(); 
mapper.writeValue(sw, t); 
System.out.println(sw.toString()); 

輸出

{"code":"c","description":"d","raw-value":"e"}