java修改数据库中的数据时出现问题，该怎么解决？

Question

修改数据库中的数据出现问题，该怎么解决？

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 'condition=1 where id = 3' at line 1
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.Util.getInstance(Util.java:381)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3515)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3447)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2554)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1761)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2046)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1964)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1949)
    at servlet.Admin.repair.updateRepair.doGet(updateRepair.java:43)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:832)
```java
@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        Connection connection=null;
        PreparedStatement pst=null;
        int r=0;
        String sql="update repair set condition=? where id = ?";
//        前端数据
        String id=req.getParameter("id");
//        类型转换
        int id1=Integer.parseInt(id);
        System.out.println("updateRepair界面已调用！");
        System.out.println("前台传来的id："+id1);
        
        connection=JDBCUtils.getConnection();
        pst=JDBCUtils.getPreparedStatement(sql);
        try {
            pst.setInt(1, 1);
            pst.setInt(2, id1);
            r=pst.executeUpdate();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{//资源释放
            JDBCUtils.release(connection, pst, null);
        }
        JSONObject json= new JSONObject();
        json.put("slist",r);
        resp.setContentType("text/json;charset=utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.getWriter().println(json);
    }

```

Answer 1

condition是mysql的预留字(关键字)，在sql语句中做为表名或字段名使用时需要用反引号包裹。代码修改如下：

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  // TODO Auto-generated method stub
  Connection connection=null;
  PreparedStatement pst=null;
  int r=0;
  String sql="update `repair` set `condition`=? where id = ?";
  //        前端数据
  String id=req.getParameter("id");
  //        类型转换
  int id1=Integer.parseInt(id);
  System.out.println("updateRepair界面已调用！");
  System.out.println("前台传来的id："+id1);
        
  connection=JDBCUtils.getConnection();
  pst=JDBCUtils.getPreparedStatement(sql);
  try {
    pst.setInt(1, 1);
    pst.setInt(2, id1);
    r=pst.executeUpdate();
  } catch (SQLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }finally{//资源释放
    JDBCUtils.release(connection, pst, null);
  }
  JSONObject json= new JSONObject();
  json.put("slist",r);
  resp.setContentType("text/json;charset=utf-8");
  resp.setCharacterEncoding("utf-8");
  resp.getWriter().println(json);
}