SpringMVC集成Hibernate返回json出现异常

查询返回json时出现的错误，json解析使用jackson

1.      问题描述

实体如下：

Classify(分类)：

         @Entity
public
classClassify {
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   private Integer
classifyId;
   private String
classifyName;
   private Integer
classifyParentId;
   public Integer getClassifyId(){
      return
classifyId;
   }
   public
void setClassifyId(IntegerclassifyId) {
      this.classifyId = classifyId;
   }
   public StringgetClassifyName() {
      return
classifyName;
   }
   public
void setClassifyName(StringclassifyName) {
      this.classifyName = classifyName;
   }
   public IntegergetClassifyParentId() {
      return
classifyParentId;
   }
   public
voidsetClassifyParentId(Integer classifyParentId) {
      this.classifyParentId =classifyParentId;
   }
 
}

 

Note(笔记):

   @Entity
public
classNote {
 
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   private Integer
noteId;
   private String
noteTime;
   @ManyToOne(fetch=FetchType.LAZY)
   @JoinColumn(name="classifyId")
   private Classify
classify;
   private String
keywords;
   private String
noteName;
   private String
noteContent;
   private String
noteSummary;

}

 

Note与Classify的关系是：多对一的关系

然后再Controller中获取指定noteId的Note

@RequestMapping(value =
"/query/{id}", method = RequestMethod.GET) 

   public Note queryNoteById(@PathVariable("id") Integer id){ 

      log.info(id+"");
      Notenote = null;
      try {
         note= noteService.queryNote(id);
         note.getClassify().getClassifyId();
      }catch(Exception e) {
         log.error("查找id为" + id
+ "的笔记出现异常", e);
      }
       return note; 

   }

 

因为1那端是使用的时候才加载，这时候，访问…/query/2,会出现异常

com.fasterxml.jackson.databind.JsonMappingException:No serializer found for classorg.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no propertiesdiscovered to create BeanSerializer (to avoid exception, disableSerializationFeature.FAIL_ON_EMPTY_BEANS)
) (through reference chain:com.pan.entity.dbentity.Note["classify"]->com.pan.entity.dbentity.Classify_$$_javassist_1["handler"])
com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59)
 

如果1那端不是懒加载，那么则不会出现异常

@ManyToOne(fetch=FetchType.EAGER)
   @JoinColumn(name="classifyId")
   private Classify
classify;

 

解决方案：

在关联实体类上标注@JsonIgnoreProperties注释

这里在Classify类上定义@JsonIgnoreProperties注释

 
@JsonIgnoreProperties(value={"hibernateLazyInitializer","handler"}) 

publicclassClassify {

   。。。

}

 

上面两个值是必须的