java - 我卡住了，我无法从 JDBC 将数据插入 MySQL 数据库

Question

我想做简单的注册表单，但我无法继续，我已经尝试了所有方法，但仍然不起作用这是我的代码:

protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException
    {
        StringBuilder builder= new StringBuilder();
        Reader reader=request.getReader();
        int c;
        while ((c=reader.read())!=-1)
        {
            builder.append((char) c);
        }
        String signup=builder.toString();
        try {
            JSONObject object= new JSONObject(signup);
            String name=object.getString("username");
            String email=object.getString("email");
            String pass=object.getString("pass");
            String sql="INSERT INTO user_f VALUES("+email+","+name+","+pass+")"+";";

            statement.executeUpdate(sql);
            //ResultSet set= statement.executeQuery("SELECT ")

        } catch (JSONException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }

我的错误堆栈我编辑了很多次代码，我对我遇到的错误感到有点沮丧:

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 '@gmail.com,dsf,sdfsd)' at line 1
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
    at com.mysql.jdbc.Util.getInstance(Util.java:387)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:939)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2547)
    at com.mysql.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1541)
    at com.mysql.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2605)
    at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1469)
    at com.herda.app.Servlet.doPost(Servlet.java:56)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

如错误所述，您的 MySQL 查询没有有效的语法。您需要在字符串文字周围加上引号。尝试这样的事情:

String sql = "INSERT INTO user_f VALUES(\"" + email + "\", \"" + name + "\", \"" + pass + "\");";

但是，请注意这段代码对 SQL 注入(inject)是开放的!要解决此安全问题，您可以使用准备好的语句。这也为您解决了报价问题。