我试图使用java和jsp中的一些类从Mysql中的数据库打印一些数据。这是我第一次这么做。我搜了很多东西，但没有任何帮助。这是我的代码：
index.html索引
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Index</title>
</head>
<body>
<form action="DB_results.jsp">
<input type = "submit" value = "Database">
</form>
</body>
</html>
绘图.java
package DB_draw;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class Draw {
ResultSet myRs;
public ResultSet getMyRs() {
return myRs;
}
public void setMyRs() {
try{
Class.forName("com.mysql.jdbc.Driver");
Connection myConn = DriverManager.getConnection("jdbc:mysql://localhost:3306/tst","root","");
Statement myStmt = myConn.createStatement();
this.myRs = myStmt.executeQuery("select * from tst.people");
while (this.myRs.next())
{
System.out.println(this.myRs.getString("onoma") + " " + this.myRs.getString("epitheto") + " " + this.myRs.getInt("id"));
}
}
catch (Exception e) {
e.printStackTrace();
}
}
}
数据库结果.jsp
<%@page import="java.sql.ResultSet"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.io.*,java.util.*,java.sql.*"%>
<%@ page import="javax.servlet.http.*,javax.servlet.*" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix="sql"%>
<%@ page import="DB_draw.*" %>
<jsp:useBean id="DB_draw" class="DB_draw.Draw" scope="session" />
<jsp:setProperty name="DB_draw" property="*"/>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Database</title>
</head>
<body style="background-color:black">
<div style = "color:yellow; font-family:fantasy; font-size:30px">
<%
ResultSet myRs = DB_draw.getMyRs();
if(myRs == null) out.println("Problem");
else
while(myRs.next())
{
out.println(myRs.getString("onoma") + " " + myRs.getString("epitheto") + " " + myRs.getInt("id"));
}
%>
</div>
</body>
</html>
问题是，当我尝试使用变量myRs在DB_results.jsp中打印结果时，myRs==NULL。为什么会这样？我正在使用Tomcat Apache 8.0。
最佳答案
你从不打电话给setMyRS()。即使这样，setMyRS()也会遍历resultset，因此myRs.next()在JSP中总是返回false。