文件存入MYSql表的blob
向MYSql的数据表中存入文件，这看似没有什么大问题，只要把文件存入longblob字段就行了。但是最近的实践发现看似简单的背后其实有很多陷阱。下面就来分享一下我遇到的问题及我的解决办法。
分类管理
先介绍一下我的应用，只有两个页面upload.jsp和download.jsp。upload.jsp使用common file upload来上传文件，并将文件存入mysql的数据表的longblob字段。download.jsp则是从数据库中取出该longblob字段的内容，并写到浏览器客户端。数据库的连接我选用tomcat的连接池，url为jdbc:mysql://localhost:3306/test?characterEncoding=gbk。jsp页面的编码都为gbk。数据表的结构如下
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version forthe right syntax to use near '??2??2è???é?±è|‘?Y:r8é§é?￥\"R??§?^è?è|??????§??????????‰-??|;?o é?aè?‘t>' at line 1sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)java.lang.reflect.Constructor.newInstance(Constructor.java:513)com.mysql.jdbc.Util.handleNewInstance(Util.java:411)com.mysql.jdbc.Util.getInstance(Util.java:386)com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3597)com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3529)com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1990)com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2151)com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2625)com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2119)com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2415)com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2333)com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2318)org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeUpdate(DelegatingPreparedStatement.java:105)org.apache.tomcat.dbcp.dbcp.DelegatingPreparedStatement.executeUpdate(DelegatingPreparedStatement.java:105)org.apache.jsp.saveFile2Mysql_jsp._jspService(saveFile2Mysql_jsp.java:111)org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)javax.servlet.http.HttpServlet.service(HttpServlet.java:717)org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
?查资料发现问题的根源在连接数据库时使用的字符编码，将url由 jdbc:mysql://localhost:3306/test?characterEncoding=gbk改成url为jdbc:mysql://localhost:3306/test?characterEncoding=utf8问题就解决了。
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