servler链接数据库有关问题求解答！

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//注册处理页面
package user;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.sql.*;
public class uregcl extends HttpServlet{
public void doPost(HttpServletRequest req,HttpServletResponse res){
res.doGet(req,res);
}
public void doGet(HttpServletRequest req,HttpServletResponse res){
Connection ct=null;
Statement st=null;
ResultSet rs=null;
try{
res.setContentType("text/html;charset=gbk");
PrintWriter pw=res.getWriter();
//用户名
String userId=(String)req.getParameterNames("userId");
//姓名
String userName=(String)req.getParameterNames("userName");
//性别
String userSex=(String)req.getParameterNames("userSex");
//年龄
int userAge=(int)req.getParameterNames("userAge");
//问题
String userQuestion=(String)req.getParameterNames("userQuestion");
//答案
String userAnswer=(String)req.getParameterNames("userAnswer");
//密码
String userPassword=(String)req.getParameterNames("userPassword");
//邮箱
String userEmail=(String)req.getParameterNames("userEmail");
//加载驱动
Class.forName("com.mysql.jdbc.Driver");
String str="insert into user(userID,userPassword,userName,userSex,userAge,userEmail,userQuestion,userAnswer) values('"+userID+"','"+userPassword+"','"+userName+"','"+userSex+"','"+userAge+"','"+userEmail+"','"+userQuestion+"','"+userAnswer+"')";
Connection ct=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306","root","123456");
Statement st=ct.createStatement();
ResultSet rs=st.executeUpdate(str);
}catch(Exception ex){
ex.printStackTrace();
}final{
//不管是否抛出异常都会执行
try{
//分别判断是否为空
//不为空时关闭资源
if(rs!=null){
rs.close();
}
if(st!=null){
st.close();
}
if(ct!=null){
ct.close();
}
}catch(Exception ex){

ex.printStackTrace();
}
}
}

特别是这句：
String str="insert into user(userID,userPassword,userName,userSex,userAge,userEmail,userQuestion,userAnswer) values('"+userID+"','"+userPassword+"','"+userName+"','"+userSex+"','"+userAge+"','"+userEmail+"','"+userQuestion+"','"+userAnswer+"')";
Connection ct=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306","root","123456");
这个又是单引号又是双引号怎么算的，还是没太明白数据库 MySQL servlet
[解决办法]


import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class Urcgcl extends HttpServlet {

    /**
     * Constructor of the object.
     */
    public Urcgcl() {
        super();
    }

    /**
     * Destruction of the servlet. &lt;br&gt;
     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }

    /**
     * The doGet method of the servlet. &lt;br&gt;
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out 
 
                .println("&lt;!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\"&gt;");
        out.println("&lt;HTML&gt;");
        out.println("  &lt;HEAD&gt;&lt;TITLE&gt;A Servlet&lt;/TITLE&gt;&lt;/HEAD&gt;");
        out.println("  &lt;BODY&gt;");
        out.print("    This is ");
        out.print(this.getClass());
        out.println(", using the GET method");
        out.println("  &lt;/BODY&gt;");
        out.println("&lt;/HTML&gt;");
        out.flush();
        out.close();
        
        
        Connection ct=null;
        Statement st=null;
        ResultSet rs=null;
        try{
        //用户名
       String userId=(String)request.getParameter("userId");
        //姓名
       String userName=(String)request.getParameter("userName");
        //性别
       String userSex=(String)request.getParameter("userSex");
        //年龄
       String userAge= request.getParameter("userAge");
        //问题
       String userQuestion=(String)request.getParameter("userQuestion");
        //答案
           String userAnswer=(String)request.getParameter("userAnswer");
            //密码
       String userPassword=(String)request.getParameter("userPassword");
        //邮箱
       String userEmail=(String)request.getParameter("userEmail");
        //加载驱动
       Class.forName("com.mysql.jdbc.Driver");
        String str="insert into user(userID,userPassword,userName,userSex,userAge,userEmail,userQuestion,userAnswer) values('"+userId+"','"+userPassword+"','"+userName+"','"+userSex+"','"+userAge+"','"+userEmail+"','"+userQuestion+"','"+userAnswer+"')";
            ct=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306","root","123456");
           st=ct.createStatement();
            int i = st.executeUpdate(str); 
       }catch(Exception ex){
        ex.printStackTrace();
        }finally{
                  //不管是否抛出异常都会执行 
 
                     try{
                          //分别判断是否为空
                              //不为空时关闭资源
                        if(rs!=null){
                            rs.close();
                                       }
                             if(st!=null){
                              st.close();
                                  }
                           if(ct!=null){
                               ct.close();
                                     }
                              }catch(Exception ex){
                             ex.printStackTrace();
                             }
                                 }
    }

    /**
     * The doPost method of the servlet. &lt;br&gt;
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred 
 
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        this.doGet(request,response);
    }

    /**
     * Initialization of the servlet. &lt;br&gt;
     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }

}

一堆的错误。
[解决办法]
你还不如用PreparedStatement来进行操作。看着这么多的格式就纠结啦
[解决办法]
单引就是数据库存储字符串必须的修饰符,双引表示字符串相加。最后生成出来是这样
('2344','密码','用户名','男',)
[解决办法]
我觉得你先要了解一下sql知识，然后了解一下servlet知识，再了解一下jdbc只是就可以了！
你写的意思就是插入数据，你可能要组装你的sql，所以要传你的参数值！呵呵，没事慢慢来，你可以用preparedstatment，就不会那么纠结！
[解决办法]
其实就是拼字符串
"insert into user(userID,userPassword,userName,userSex,userAge,userEmail,userQuestion,userAnswer) values('"+userID+"','"+userPassword+"','"+userName+"','"+userSex+"','"+userAge+"','"+userEmail+"','"+userQuestion+"','"+userAnswer+"')"
可以把这个字符串用+分开

第一个“”里面就是个普通的字符串然后+userId userId是一个值比如是1

结果就是
insert into user(userID,userPassword,userName,userSex,userAge,userEmail,userQuestion,userAnswer) values(' 1
后面的类似
[解决办法]
我也感觉preparedstatment可能会好一点，首先sql语句的格式就很清晰，然后是效率问题，预编译的，如果要多次执行这类语句的话，效率也会好一些，然后还可以防止sql注入。
[解决办法]

引用:

引用:你还不如用PreparedStatement来进行操作。看着这么多的格式就纠结啦
我看到有些不加引号，像单独的写语句一样也行
就是比如
insert into user('a','b','c') values('s1','s2','s3');这样。

其实你把你拼成的字符串打印出来，然后控制台里面显示的与你在命令行模式下执行的语句一样就行。
就像是单引号 ' 。你在命令行敲的时候肯定要敲上去吧。那么你在拼字符串的时候，就要把那个'（单引号）拼到那个sql中。

servler链接数据库有关问题求解答！

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