我将servlet变量传递给jsp时遇到了麻烦 .
当然,我也已经为servlet设置了web.xml
<servlet>
<servlet-name>databaseServlet</servlet-name>
<servlet-class>Servlet.databaseServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>databaseServlet</servlet-name>
<url-pattern>/dbServlet</url-pattern>
</servlet-mapping>
结果是所有的名称,所有者,物种和性别值都为空 . 有人可以帮我弄这个吗?谢谢
P.S:我也试过在servlet中使用request.getSession() . setAttribute,也没用
P.P.S:如果我做出以下改变:
databaseServlet.java
package Servlet;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.ArrayList;
@SuppressWarnings("serial")
public class databaseServlet extends HttpServlet {
private Connection conn;
private Statement statement;
String name;
String owner;
String species;
String sex;
String birth;
String death;
public void init(ServletConfig config) throws ServletException {
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(
"jdbc:mysql://localhost/STUDENTS",
"root",
"");
statement = conn.createStatement();
String sql = "SELECT name, owner, species, sex, birth, death FROM pet";
ResultSet rs = statement.executeQuery(sql);
//STEP 5: Extract data from result set
while(rs.next()){
//Retrieve by column name
name = rs.getString("name");
owner = rs.getString("owner");
species = rs.getString("species");
sex = rs.getString("sex");
birth = rs.getString("birth");
death = rs.getString("death");
}
rs.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setAttribute("NAME", "Hello");
System.out.println(name);
request.setAttribute("OWNER",owner);
request.setAttribute("SPECIES",species);
request.setAttribute("SEX", sex);
RequestDispatcher dispatcher=getServletConfig().getServletContext().getRequestDispatcher("/dbServlet.jsp");
dispatcher.forward(request, response);
}
}
这是我的新jsp:
<body>
Name="${databaseServlet.NAME}"
Owner="${databaseServlet.OWNER}"
Species="<%= request.getAttribute("SPECIES") %>"
Sex="<%= request.getSession().getAttribute("SEX") %>"
</body>
Name和Owner都返回空字符串,而Species和Sex仍然返回NULL
基本上我要做的是访问MySQL数据库以从表中检索变量,并使用JSP显示它
3 回答
只需为您的属性提供范围,您就可以像这样更改代码:
当你处理属性时,使sessionScope像:
我希望这可以帮助你 .
尝试使用
我想它应该有效 . 并且仅使用request.getAttribute(),它将返回Object类型,您必须将其强制转换
在
doPost
方法中设置请求属性时,请确保您具有name
,owner
,species
和sex
的有效值 .使用EL语法
Do not write scriptlets in JSP ,因为Scriptlet不应该在JSP中使用超过十年 . 学习JSP EL,JSTL,并使用servlet作为Java代码 . How to avoid Java Code in JSP-Files?