mysql blob 写入表_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。

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

CREATE TABLE `file` (

`id` int(11) NOT NULL AUTO_INCREMENT,

`filename` varchar(255) CHARACTER SET utf8 NOT NULL,

`content` longblob,

`filetype` varchar(255) CHARACTER SET utf8 NOT NULL,

`size` int(11) DEFAULT NULL,

`ip` varchar(255) CHARACTER SET utf8 NOT NULL,

`date` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' ON UPDATE CURRENT_TIMESTAMP,

PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=gbk

上传文件的java代码如下

request.setCharacterEncoding("gbk");

if("POST".equalsIgnoreCase(request.getMethod())){

DiskFileUpload upload = new DiskFileUpload();

upload.setHeaderEncoding("gbk");

List list = upload.parseRequest(request);

for(FileItem fileItem : list){

if(!fileItem.isFormField()){

String filename = fileItem.getName().replace("\\", "/");

filename = filename.substring(filename.lastIndexOf("/") + 1);

Context envContext = (Context)new InitialContext().lookup("java:/comp/env");

DataSource ds = (DataSource) envContext.lookup("mysqlTest");

Connection conn = ds.getConnection();

PreparedStatement preStmt = conn.prepareStatement("insert into file (filename, filetype, size, content, ip, date) values (?,?,?,?,?,?)");

preStmt.setString(1, filename);

preStmt.setString(2, fileItem.getContentType());

preStmt.setInt(3, (int)fileItem.getSize());

preStmt.setString(5, request.getRemoteAddr());

preStmt.setTimestamp(6, new Timestamp(System.currentTimeMillis()));

preStmt.setBinaryStream(4, fileItem.getInputStream(),(int)fileItem.getSize());

preStmt.executeUpdate();

preStmt.close();

conn.close();

}

下载文件的代码如下

Context envContext = (Context)new InitialContext().lookup("java:/comp/env");

DataSource ds = (DataSource) envContext.lookup("mysqlTest");

conn = ds.getConnection();

preStmt = conn.prepareStatement("select * from file where id = ?");

preStmt.setInt(1, id);

rs = preStmt.executeQuery();

if(rs.next()){

response.reset();

response.setContentType(rs.getString("filetype"));

response.setContentLength(rs.getInt("size"));

InputStream ins = null;

OutputStream ous = null;

try{

ins = rs.getBinaryStream("content");

ous = response.getOutputStream();

byte[] b = new byte[1024];

int len = 0;

while((len = ins.read(b))!= -1){

ous.write(b, 0, len);

}

}finally{

if(ous != null) ous.close();

if(ins != null) ins.close();

}

开始上传一些文本文件没问题，但是当上传的文件大于1M时就报出如下异常

com.mysql.jdbc.PacketTooBigException: Packet for query is too large (5553258 > 1048576). You can change this value on the server by setting the max_allowed_packet' variable.

com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3279)

com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1971)

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.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)

为了解决这个问题，没少废了周折。在网上看到一些解决办法，但是在我这都不起作用。在Mysql的安装装目录的my.ini文件的【mysqld】节点下添加max_allowed_packet=100M，重启mysql服务后(可用net stop/start mysql)，在mysql客户端查看时show variables llike “%packet%”，显示max_allowed_packet 的大小依然是1M。用mysqld --max_allowed_packet=100M结果依然如此。经过不断尝试发现了一个问题mysqld启动后会成为一个后台运行的进程，当已经有一个mysqld进程在运行时，再次调用mysqld将会被忽略。所以正确的做法是，首先关闭mysql服务，然后查看windows的任务管理器，关闭正在运行的mysqld进程(如果存在)，然后再用mysqld --max_allowed_packet=100M来启动就没有问题了。然而这个办法在机器重启之后就没有效果了，开机启动所使用的max_allowed_packet如何改没有找到解决办法。

解决了上个问题，在上传MP3文件时又遇到了一个异常，同样让人头痛，异常信息如下

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for

the right syntax to use near 'ç„²æ‹²è¬�?éž±è¦‘?Y:r8é–§é‡¥\"Rãˆ§?^è–‡è¦†çšŸç®§ç»Ÿå»œçŸ»å‰æ„¦;äº é‚ªè¶‘t>' at line 1

sun.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)