Spring Boot搭建Restful API输出Json数据异常

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背景

在使用SpringBoot搭建RESTful API时，在没有实体关联关系时一切正常，但在实体类中加入实体关联时，当MyBatis查询出数据实体类使用jackson序列化为json时，返回页面的时候报如下错误：


2017-08-07 11:18:33.007  WARN 12332 --- [nio-9091-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"])
2017-08-07 11:18:33.002 DEBUG 12332 --- [nio-9091-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : Resolving exception from handler [public java.util.Map com.iws.web.api.RecordApiController.selectByAccountId(java.lang.String,java.lang.String,java.lang.String)]: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"])
2017-08-07 11:18:33.003 DEBUG 12332 --- [nio-9091-exec-1] .w.s.m.a.ResponseStatusExceptionResolver : Resolving exception from handler [public java.util.Map com.iws.web.api.RecordApiController.selectByAccountId(java.lang.String,java.lang.String,java.lang.String)]: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"])
2017-08-07 11:18:33.004 DEBUG 12332 --- [nio-9091-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolving exception from handler [public java.util.Map com.iws.web.api.RecordApiController.selectByAccountId(java.lang.String,java.lang.String,java.lang.String)]: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.ibatis.executor.loader.javassist.JavassistProxyFactory$EnhancedResultObjectProxyImpl and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.HashMap["data"]->java.util.ArrayList[0]->com.iws.model.Record_$$_jvst129_0["handler"])

解决方法

在关联类中引用 @JsonIgnoreProperties注解，并将类中关联到的类加到注解的value值里面去。


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

其中 handler必须添加!

此处暂时不明白 headler在何处转化，查资料显示 @JsonIgnore注解跟 @JsonIgnoreProperties作用一致，但无法对 handler进行注解。

附相关注解解释

@Transient

@Transient表示该属性并非一个到数据库表的字段的映射,ORM框架将忽略该属性；如果一个属性并非数据库表的字段映射，就务必将其标示为 @Transient，否则ORM框架默认其注解为 @Basic；


//表示该字段在数据库表中没有
@Transient
private Account account;

@JsonIgnoreProperties

此注解是类注解，作用是 json序列化时将 java bean中的一些属性忽略掉，序列化和反序列化都受影响。


@JsonIgnoreProperties(value = {"handler", "account"})
public class Record {
    private Account account;
}

@JsonIgnore

此注解用于属性或者方法上（最好是属性上），作用和上面的 @JsonIgnoreProperties一样。


public class Record {
    @JsonIgnore
    private Account account;
}

@JsonFormat

此注解用于属性或者方法上（最好是属性上），可以方便的把 Date类型直接转化为我们想要的模式，比如


@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")
private Date date;

@JsonSerialize

此注解用于属性或者 getter方法上，用于在序列化时嵌入我们自定义的代码，比如序列化一个 double时在其后面限制两位小数点。

@JsonDeserialize

此注解用于属性或者 setter方法上，用于在反序列化时可以嵌入我们自定义的代码，类似于上面的 @JsonSerialize