用JDBC向MySQL插入一条数据

原先的做法：jsp页面传递参数username,userzhuanye,userxingbie

//增加方法
public void dbZengJia(Statement stmt,String username,String userzhuanye,String userxingbie){
   String sql="insert into person(name,zhuanye,xingbie)values (?,?,?)";
   try {
    stmt.executeUpdate("insert into person(name,zhuanye,xingbie) values ('username','$userzhuanye','$userxingbie')");
   } catch (SQLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
//   }
}

console报错：

com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: Unknown column 'userid' in 'field list'
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2870)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3170)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1316)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1235)
at com.DBConnection.dbZengJia(DBConnection.java:66)
at com.zengjia.doPost(zengjia.java:90)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)

经过研究发现JDBC对SQL语句的语法冲突无法理解，改进做法如下：

关键是怎家了预编译来回避语法冲突的问题

public void dbZengJia(Statement stmt,String username,String userzhuanye,String userxingbie){
   String sql="insert into person(name,zhuanye,xingbie)values (?,?,?)";
   try {
    //预编译，防止出现语法冲突
    PreparedStatement pstmt=conn.prepareStatement(sql);
    pstmt.setString(1, username);
    pstmt.setString(2, userzhuanye);
    pstmt.setString(3, userxingbie);
    pstmt.executeUpdate();
   } catch (SQLException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
   }

}