JDBC:从数据库中取数据的一个bug

先看错误信息：

 1 java.sql.SQLException: Before start of result set
 2     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
 3     at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.java:720)
 4     at com.mysql.jdbc.ResultSet.getStringInternal(ResultSet.java:5624)
 5     at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5544)
 6     at hw5servlet.doGet(hw5servlet.java:38)
 7     at hw5servlet.doPost(hw5servlet.java:62)
 8     at javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
 9     at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
10     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
11     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
12     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
13     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
14     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
15     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
16     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
17     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
18     at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:879)
19     at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:617)
20     at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1760)
21     at java.lang.Thread.run(Thread.java:745)

再看编写的JDBC查看代码（如下）：

 1 Class.forName("com.mysql.jdbc.Driver");
 2             Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/day36","root","root");                    
 3             String insertString="select password from register where email="+email+";";
 4             //String insertString="insert into  register values(?,?,?)";
 5             //System.out.println("hw5servlet.doGet()"+insertString);
 6             Statement ps = connection.createStatement();
 7             boolean execute = ps.execute(insertString);
 8             //ps.executeQuery(insertString);
 9             if(execute){
10                 ResultSet rs = ps.getResultSet();
11                 //rs.beforeFirst();
12                 //rs.next();
　　　　　　　　　　　　//本以为从数据库中去代码只有一行，默认应该是在第一行的，然后直接rs.getString(1)就可以。
                  //但事实不然，getString()时一定要有rs.next().

13                 String password1 = rs.getString(1);
14                 System.out.println("hw5servlet.doGet()"+password1);
15                 if(password.equals(password1)){
16                     response.getWriter().write("登陆成功");
17                 }else {
18                     response.getWriter().write("密码错误，请重新登录");
19                     response.sendRedirect("/Day36_JDBC_hw4/index.jsp");
20                 }    
21             }

找了许久没找到，然后百度：http://blog.csdn.net/killua_hzl/article/details/6073618

posted @ 2016-02-18 21:21  鸡毛落一地  阅读(293)  评论(0)  编辑  收藏  举报