问题描述：

在网站底部进行评论，点击提交按钮时，后台tomcat报错，通过火狐浏览器的firebug看到发送的POST请求体中，有一个title参数是乱码，

导致该字段超长违反了数据库字段的长度约束：

这个title字段的应该是文章的标题（中文）：

tomcat报错信息：

2017-06-15 16:15:50,448 DEBUG [modules.cms.dao.CommentDao.findList] - <==      Total: 1============乱码部分内容===========中央第åä¸å·¡è§ ç»åé西çå§åé¦å·¡ è§&ldquo;å头ç&rdquo;æåµ2017-06-15 16:17:12,911 DEBUG [modules.cms.dao.CommentDao.get] - ==>  Preparing: SELECT a.id AS "id", a.category_id AS "category.id", a.content_id AS "contentId", a.title AS "title", a.content AS "content", a.name AS "name", a.ip AS "ip", a.create_date AS "createDate", a.audit_user_id AS "auditUser.id", a.audit_date AS "auditDate", a.del_flag AS "delFlag" FROM cms_comment a WHERE a.id = ? 2017-06-15 16:17:12,912 DEBUG [modules.cms.dao.CommentDao.get] - ==> Parameters: 0(String)2017-06-15 16:17:12,913 DEBUG [modules.cms.dao.CommentDao.get] - <==      Total: 02017-06-15 16:17:12,917 DEBUG [modules.cms.dao.CommentDao.insert] - ==>  Preparing: INSERT INTO cms_comment( id, category_id, content_id, title, content, name, ip, create_date, audit_user_id, audit_date, del_flag ) VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? ) 2017-06-15 16:17:12,924 DEBUG [modules.cms.dao.CommentDao.insert] - ==> Parameters: 　　dd82abcfbd4d4176b8400dce7b8a0dd0(String), 　　106c3f5a9d354d69946304ba1003e85e(String), 　　9948c62c9ab4491daadccfe23032534b(String), 　　中央第åä¸å·¡è§ 　　ç»åé西çå§åé¦å· 　　¡è§&ldquo;å头ç&rdquo;æåµ(String), 　　测试评论(String), 　　小李(String), 　　0:0:0:0:0:0:0:1(String), 　　2017-06-15 16:17:12.916(Timestamp), 　　null, 　　null, 　　2(String) 2017-06-15 16:17:13,035 ERROR [500.jsp] - ### Error updating database.  Cause: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'title' at row 1### The error may involve defaultParameterMap### The error occurred while setting parameters### SQL: INSERT INTO cms_comment(    id,    category_id,    content_id,    title,    content,    name,    ip,    create_date,    audit_user_id,    audit_date,    del_flag   ) VALUES (    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?   )### Cause: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'title' at row 1; SQL []; Data truncation: Data too long for column 'title' at row 1; nested exception is com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'title' at row 1org.springframework.dao.DataIntegrityViolationException: ### Error updating database.  Cause: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'title' at row 1### The error may involve defaultParameterMap### The error occurred while setting parameters### SQL: 　　　　INSERT INTO cms_comment(id,    category_id,    content_id,    title,    content,    name,    ip,    create_date,    　　　　　　　　　　　　　　　　　　audit_user_id,    audit_date,    del_flag   ) 　　　　VALUES (    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?,    ?   )### Cause: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'title' at row 1; SQL []; Data truncation: Data too long for column 'title' at row 1; nested exception is com.mysql.jdbc.MysqlDataTruncation: 　　　　　　　　　　　　　　 Data truncation: Data too long for column 'title' at row 1    at org.springframework.jdbc.support.SQLStateSQLExceptionTranslator.doTranslate(SQLStateSQLExceptionTranslator.java:102)    at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:73)    at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)    at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:74)    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:399)    at com.sun.proxy.$Proxy27.insert(Unknown Source)

通过提示可以看出，执行SQL语句时报字段超长的错误，文章的中文标题在乱码之后，超出了title字段所允许的长度，因为数据库中title字段的长度为255：

 

解决办法：

打开tomcat的conf目录下的server.xml文件，在Connector标签中添加 URIEncoding="utf-8" 即可：

 

重启tomcat，再次测试，评论提交成功，也不再乱码了：

 

附jsp页面中EL表达式取值部分代码：

 

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