GSON 报错HibernateProxy. Forgot to register a type adapter? 的解决办法
使用Gson转换hibernate对象遇到一个问题，当对象的Lazy加载的，就会出现上面的错误。处理方式摘抄自网上，留存一份以后自己看。
网上找到的解决办法,首先自定义一个类继承TypeAdapter:
1 package cn.xjy.finance.loanapply.utils ; 2 3 import java.io.IOException ; 4 import org.hibernate.Hibernate ; 5 import org.hibernate.proxy.HibernateProxy ; 6 import com.google.gson.Gson ; 7 import com.google.gson.TypeAdapter ; 8 import com.google.gson.TypeAdapterFactory ; 9 import com.google.gson.reflect.TypeToken ; 10 import com.google.gson.stream.JsonReader ; 11 import com.google.gson.stream.JsonWriter ; 12 13 /** 14 * This TypeAdapter unproxies Hibernate proxied objects, and serializes them 15 * through the registered (or default) TypeAdapter of the base class. 16 */ 17 public class HibernateProxyTypeAdapter extends TypeAdapter<HibernateProxy> { 18 19 public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() { 20 @Override 21 @SuppressWarnings("unchecked") 22 public <T> TypeAdapter<T> create(Gson gson, 23 TypeToken<T> type) { 24 return (HibernateProxy.class 25 .isAssignableFrom(type 26 .getRawType()) ? (TypeAdapter<T>) new HibernateProxyTypeAdapter( 27 gson) : null) ; 28 } 29 } ; 30 31 private final Gson context ; 32 33 private HibernateProxyTypeAdapter(Gson context) { 34 this.context = context ; 35 } 36 37 @Override 38 public HibernateProxy read(JsonReader in) throws IOException { 39 throw new UnsupportedOperationException("Not supported") ; 40 } 41 42 @SuppressWarnings({ "rawtypes", "unchecked" }) 43 @Override 44 public void write(JsonWriter out, HibernateProxy value) throws IOException { 45 if (value == null) { 46 out.nullValue() ; 47 return ; 48 } 49 // Retrieve the original (not proxy) class 50 Class<?> baseType = Hibernate.getClass(value) ; 51 // Get the TypeAdapter of the original class, to delegate the 52 // serialization 53 TypeAdapter delegate = context.getAdapter(TypeToken.get(baseType)) ; 54 // Get a filled instance of the original class 55 Object unproxiedValue = ((HibernateProxy) value).getHibernateLazyInitializer() 56 .getImplementation() ; 57 // Serialize the value 58 delegate.write(out, unproxiedValue) ; 59 } 60 }
然后初始化gson对象的方式:
1 Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd") 2 .registerTypeAdapterFactory( 3 HibernateProxyTypeAdapter.FACTORY).create() ;
这样就解决了,出现这个错误的主要原因是,hibernate采取懒加载的方式查询数据库,也就是只有用到了才去查真正的数据,用不到的话只是返回一个代理对象,gson识别不了代理对象,所以没法转换.
