GSON -JSON 反序列化-多节点名称支持

引言.最近对接支付宝支付时,发现支付宝接口返回一个泛型的对象.如{"XXX_YYY_response":{},"sign":"AFDSS#QR@43211423142341FAF"},其中 XXX_YYY_response 是动态变化的,即多个值映射到泛型字段.

GSON 提供了 @SerializeName注解来实现.

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD})
public @interface SerializedName {
 
/**
* @return the desired name of the field when it is serialized or deserialized
*/
String value();
/**
* @return the alternative names of the field when it is deserialized
*/
String[] alternate() default {};
}

 

可以给 alternate 赋一个数组来实现.但是每次引入新的支付宝接口时,要变更注解字段 alternate (不能使用变量,因注解字段值必须是常量)的值.不符合开闭原则.

 

使用反射来解决.给泛型对象添加静态注册名字方法,动态改变注解alternate 的值.在具体对象反序化前可以注册一次.

public class AlipayResult<OutParameter extends AlipayBasicOutParameter> {
 
private static final Logger LOG= LoggerFactory.getLogger(AlipayResult.class);
 
@Expose
private String sign;
private static final String SIGN_TITLE_TAG="sign";
 
@Expose
@SerializedName(value="",alternate = {})
private OutParameter outParameter;
 
 
@Expose
@SerializedName("error_response")
private AlipayError errorObject;
 
 
private static final Set<String> JSON_NAMES= new HashSet<>();
 
static {
JSON_NAMES.add("error_response");
}
 
 
 
public static synchronized final void registerOutParameterAlternate(final String namespace){
try {
JSON_NAMES.add(namespace);
Field field = AlipayResult.class.getDeclaredField("outParameter");
field.setAccessible(true);
SerializedName serialName = field.getDeclaredAnnotation(SerializedName.class);
String[] ns = serialName.alternate();
for (String item : ns) {
if (item.equals(namespace)) {
return;
}
}
InvocationHandler h = Proxy.getInvocationHandler(serialName);
// 获取 AnnotationInvocationHandler 的 memberValues 字段
Field hField = h.getClass().getDeclaredField("memberValues");
// 因为这个字段事 private final 修饰，所以要打开权限
hField.setAccessible(true);
// 获取 memberValues
Map memberValues = (Map) hField.get(h);
// 修改 value 属性值
List<String> target =new ArrayList<String>();
if(null!=ns&&ns.length>0){
for (String i:ns){
target.add(i);
}
}
target.add(namespace);
String[] alternateArr = target.toArray(new String[0]);
memberValues.put("alternate", alternateArr);
if (LOG.isInfoEnabled()) {
LOG.info("alternate value is " + alternateArr);
}
}catch (Throwable throwable){
throw new RuntimeException(throwable);
}
}
 
private static final String AlipayResponseNameSpaces="";
 
public String getSign() {
return sign;
}
 
public void setSign(String sign) {
this.sign = sign;
}
 
public OutParameter getOutParameter() {
return outParameter;
}
 
public void setOutParameter(OutParameter outParameter) {
this.outParameter = outParameter;
}