解决Failed toString() invocation on an object com.alibaba.fastjson.JSONException: write javaBean error

淡淡的烟草味﹌ 2023-09-28 21:14 20阅读 0赞

#### 文章目录 ####

*  1. 复现问题
 *  2. 分析问题
 *  3. 解决问题

## 1. 复现问题 ##

今天在启动spring boot项目，突然出现如下问题：

SLF4J: Failed toString() invocation on an object of type [com.superjson.superjsonmanager.config.jwt.JwtProperties$$EnhancerBySpringCGLIB$$3c58badf]
    Reported exception:
    com.alibaba.fastjson.JSONException: write javaBean error, fastjson version 1.2.70, class org.springframework.beans.factory.support.DefaultListableBeanFactory, fieldName : $$beanFactory, write javaBean error, fastjson version 1.2.70, class com.baomidou.mybatisplus.MybatisConfiguration, fieldName : configuration, write javaBean error, fastjson version 1.2.70, class com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceWrapper, fieldName : dataSource, write javaBean error, fastjson version 1.2.70, class com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl, fieldName : connection, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.ConnectionImpl, fieldName : connectionRaw, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.DatabaseMetaData, fieldName : metaData, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.result.ResultSetImpl, fieldName : catalogs
    	at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:539)
    	at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:149)
    	at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:333)
    	at com.alibaba.fastjson.serializer.ASMSerializer_1_JwtProperties$$EnhancerBySpringCGLIB$$3c58badf.write(Unknown Source)
    	at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:285)
    	at com.alibaba.fastjson.JSON.toJSONString(JSON.java:758)
    	at com.alibaba.fastjson.JSON.toJSONString(JSON.java:696)
    	at com.alibaba.fastjson.JSON.toJSONString(JSON.java:661)
    	at com.superjson.superjsonmanager.config.jwt.JwtProperties.toString(JwtProperties.java:73)
    	at org.slf4j.helpers.MessageFormatter.safeObjectAppend(MessageFormatter.java:277)
    	at org.slf4j.helpers.MessageFormatter.deeplyAppendParameter(MessageFormatter.java:249)
    	at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:211)
    	at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:161)
    	at ch.qos.logback.classic.spi.LoggingEvent.getFormattedMessage(LoggingEvent.java:293)
    	at ch.qos.logback.classic.spi.LoggingEvent.prepareForDeferredProcessing(LoggingEvent.java:206)
    	at ch.qos.logback.core.OutputStreamAppender.subAppend(OutputStreamAppender.java:223)
    	at ch.qos.logback.core.OutputStreamAppender.append(OutputStreamAppender.java:102)
    	at ch.qos.logback.core.UnsynchronizedAppenderBase.doAppend(UnsynchronizedAppenderBase.java:84)
    	at ch.qos.logback.core.spi.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:51)
    	at ch.qos.logback.classic.Logger.appendLoopOnAppenders(Logger.java:270)
    	at ch.qos.logback.classic.Logger.callAppenders(Logger.java:257)
    	at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:421)
    	at ch.qos.logback.classic.Logger.filterAndLog_1(Logger.java:398)
    	at ch.qos.logback.classic.Logger.info(Logger.java:583)
    	at com.superjson.superjsonmanager.SuperJsonManagerApplication.main(SuperJsonManagerApplication.java:51)
    Caused by: com.alibaba.fastjson.JSONException: write javaBean error, fastjson version 1.2.70, class com.baomidou.mybatisplus.MybatisConfiguration, fieldName : configuration, write javaBean error, fastjson version 1.2.70, class com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceWrapper, fieldName : dataSource, write javaBean error, fastjson version 1.2.70, class com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl, fieldName : connection, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.ConnectionImpl, fieldName : connectionRaw, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.DatabaseMetaData, fieldName : metaData, write javaBean error, fastjson version 1.2.70, class com.mysql.cj.jdbc.result.ResultSetImpl, fieldName : catalogs
    	at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:539)
    	at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:149)
    	at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:333)
    	at com.alibaba.fastjson.serializer.ASMSerializer_105_DefaultSqlSessionFactory.write(Unknown Source)
    	at com.alibaba.fastjson.serializer.MapSerializer.write(MapSerializer.java:271)
    	at com.alibaba.fastjson.serializer.MapSerializer.write(MapSerializer.java:44)
    	at com.alibaba.fastjson.serializer.FieldSerializer.writeValue(FieldSerializer.java:320)
    	at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:470)
    	... 24 more

上述问题总结一句话是，使用`alibaba.fastjson`解析`Javabean`对象时，出现了错误，但为什么会出现这个问题呢？

## 2. 分析问题 ##

我使用`alibaba.fastjson`解析`JwtProperties`对象报出上述错误的，该对象是用来存储`jwt`的参数，如下代码所示：

/**
     * @author zby
     * @datetime 2022/8/19 12:05
     * @desc jwt实体类，从yml配置文件中获取配置的属性
     */
    @Getter
    @Setter
    @Configuration
    @ConfigurationProperties(prefix = "jwt")
    public class JwtProperties {
        
    
        @Value("${jwt.secret}")
        private String appSecret;
    
        @Value("${jwt.expiration}")
        private long expiration;
    
        @Value("${jwt.typ}")
        private String typ;
    
        @Value("${jwt.alg}")
        private String alg;
    
        @Value("${jwt.subject}")
        private String subject;
    
        @Value("${jwt.tokenStartWith}")
        private String tokenStartWith;
    
        @Value("${jwt.tokenHeader}")
        private String tokenHeader;
    
        public String getTokenStartWith() {
        
            return tokenStartWith + " ";
        }
    
        @Override
        @JSONField(serialize = false)
        public String toString() {
        
            return JSONObject.toJSONString(this);
        }
    }

即重写`toString()`方法内部语句`JSONObject.toJSONString(this);`时出现了问题，于是断点看为何会出现这种问题，如下截图所示：

![在这里插入图片描述][43b70eb2771c43b5b39a48c83444c20a.png]

你会发现动态生成的`JwtProperties的this对象`并不是只有其属性值，而是还多了很多我并没有定义的属性值，为什么会出现这种情况呢？

应为`spring boot`采用动态代理的模式去实例化对象的，而这额外的属性值便是动态代理对象的属性值，因而，`fastjson`无法解析动态代理的属性值，故而报错。

## 3. 解决问题 ##

既然知道错误的原因是`spring boot`动态代理造成的，我们便不把对象交给`spring boot`动态代理，可以进行如下修改`toString()`方法：

@Override
    @JSONField(serialize = false)
    public String toString() {
        
      JSONObject jsonObject = new JSONObject();
      jsonObject.put("appSecret", this.appSecret);
      jsonObject.put("expiration", this.expiration);
      jsonObject.put("typ", this.typ);
      jsonObject.put("alg", this.alg);
      jsonObject.put("subject", this.subject);
      jsonObject.put("tokenStartWith", this.tokenStartWith);
      jsonObject.put("tokenHeader", this.tokenHeader);
      return JSONObject.toJSONString(jsonObject);
    }

如此启动`spring boot`即可，如下图所示：

![在这里插入图片描述][fe54863486204a7bb928e88a85f478d5.png]

[43b70eb2771c43b5b39a48c83444c20a.png]: https://img-blog.csdnimg.cn/43b70eb2771c43b5b39a48c83444c20a.png
[fe54863486204a7bb928e88a85f478d5.png]: https://img-blog.csdnimg.cn/fe54863486204a7bb928e88a85f478d5.png