网站后台开发常见BUG及解决方法

Bug-01
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C:\Program Files\MariaDB 5.5\bin>mysql -u root -p;
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (
ES)


登录时去掉最后的";"
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Bug-02 
启动tomcat 出现如下问题:


java.sql.SQLException: 
Access denied for user 'root'@'localhost' (using password: NO)


step01:检测数据库配置文件中url,用户名,密码配置是否正确


假如配置都没有问题,还出现拒绝访问,如何解决?


step02:检测数据库服务器是否已经启动?


可以从mysql的客户端先登录一下试试,假如可以登录,说明服务已经启动


step03:重新执行maven update (强制更新)


重新执行了maven update多次,启动tomcat,还是报拒绝访问问题.


step04: 尝试更新数据库驱动并检测url中的端口号.


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Bug-03 


ttm1.0 项目登录以后,页面乱码出现乱码?


解决方案:
1)查询数据库表中内容
2)假如内容是乱码,则重新导入数据


step01: set names utf8
step02: source d:/ttms.sql


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Bug-04


org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): cn.tedu.ttms.product.dao.ProjectDao.findObjects
at org.apache.ibatis.binding.MapperMethod$SqlCommand.(MapperMethod.java:189)
at org.apache.ibatis.binding.MapperMethod.




检测XxxMapping.xml文件中的内容配置是否有问题
1)namespace(命名空间)
2)resultType(映射结果类型)
3)id(值是否与dao中方法对应)


解决问题的思路:4w+h
 1)when  (执行什么操作出现的这个问题)
 2)what   (什么问题)
 3)where (哪里的问题,至少要看5行错误)
 4)why     (为什么会出现这个问题)
 5)how     (如何解决这个问题)




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Bug05


org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: No serializer found for class cn.tedu.ttms.product.entity.Project and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class cn.tedu.ttms.product.entity.Project and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0])
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:299)
at org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:106)




此问题一般是实体对象缺少get方法所导致


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Bug-06


HTTP Status 404 - /ttms1.01/WEB-INF/pages/project/doFindObjects.jsp


查找控制层对应方法是否使用了@ResponseBody注解


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Bug-07


org.mybatis.spring.MyBatisSystemException:
nested exception is org.apache.ibatis.binding.BindingException: Parameter 'startIndex' not found.
Available parameters are [0, 1, param1, param2]
atorg.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
at com.sun.proxy.$Proxy40.selectList(Unknown Source)


此异常为绑定异常,是在mybatis映射文件中通过#或$去获取startIndex的值时,没有找到这个参数,找到的是[0, 1, param1, param2].


解决方案:
1)在dao中通过@Param定义参数,mapper文件中通过
  #{startIndex}或${startIndex}
2)借助#{param1},...等形式在mapper文件中获取参数值
3)借助#{0},#{1},...等形式在mapper文件获取值.
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Bug-08
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE  valid=0' at line 1
; bad SQL grammar []; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'WHERE  valid=0' at line 1
at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:231)
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:73)


以后再遇到MySQLSyntaxErrorException时,先检测你的SQL语法.


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Bug-09 


浏览器的控制端出现:
Uncaught SyntaxError: unexpected token }


一般是JS代码中多或少了"}"