0
我正在開發一個小型的sql servlet應用程序，它接受來自html頁面文本區域的SQL命令，將該命令發送到一個使SQL連接成功的servlet，並將結果集放入一個數組列表中。我已經完成了所有這些工作，並且可以將列名打印到java servlet類中的瀏覽器中。我需要做的一件事就是使用JSP頁面將結果打印到表格中。 JSP頁面看起來就像我們第一次使用的html頁面。我無法弄清楚我將如何從servlet獲取arraylist到JSP頁面以顯示給用戶。如何將數據從servlet獲取到JSP頁面中？
下面是HTML頁面：
<html>
<head>
<title>WebApp</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body style="background-color:blue;">
<center>
<font color="white">
<h1> Welcome to the Project 4 Remote Database Management System</h1>
<hr>
You are connected to the Project4 database. <br>Please enter any valid SQL query or update statement.<br>
If no query/update command is given the Execute button will display all supplier information in the database. <br>All execution results will appear below.
<br>
<br>
<form action="NewServlet" method="post">
<textarea rows="10" cols="60"name="command"></textarea>
<br>
<button type="submit">Execute Query</button>
<button type="submit">Clear Command</button>
</form>
<hr>
<h1>Database Results</h1>
</font>
</body>
</html>
這裏是servlet代碼：
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.swing.JOptionPane;
/**
*
* @author KJ4CC
*/
public class NewServlet extends HttpServlet {
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
Connection connection;
Vector<String> columnNames = new Vector<String>();
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
/* TODO output your page here. You may use following sample code. */
String command = request.getParameter("command");
out.println("<!DOCTYPE html>");
out.println("<html>");
sqlConnection(command);
//prints out column names into the browser.
out.println(columnNames);
}
}
public void sqlConnection(String command){
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/project3";
String user = "root";
String pass = "Brandy?1994";
ResultSet rs;
try {
Class.forName(driver);
} catch (ClassNotFoundException ex) {
Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex);
}
try {
connection = DriverManager.getConnection(url,user,pass);
} catch (SQLException ex) {
Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex);
}
Statement stmt;
try {
stmt = connection.createStatement();
rs = stmt.executeQuery(command);
int colNum = rs.getMetaData().getColumnCount();
for (int i = 0; i < colNum; i++) {
columnNames.add(rs.getMetaData().getColumnLabel(i+1));
}
} catch (SQLException ex) {
Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex);
}
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Handles the HTTP <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
這裏是JSP頁面的開始：
<html>
<head>
<title>WebApp</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body style="background-color:blue;">
<center>
<font color="white">
<h1> Welcome to the Project 4 Remote Database Management System</h1>
<hr>
You are connected to the Project4 database. <br>Please enter any valid SQL query or update statement.<br>
If no query/update command is given the Execute button will display all supplier information in the database. <br>All execution results will appear below.
<br>
<br>
<form action="NewServlet" method="post">
<textarea rows="10" cols="60"name="command"></textarea>
<br>
<button type="submit">Execute Query</button>
<button type="submit">Clear Command</button>
</form>
<hr>
<h1>Database Results</h1>
<%
DO TABLE STUFF HERE TO OUTPUT SQL RESULTS
%>
</font>
</body>
</html>
我想我將創建一個javaBean來存儲數組，以便JSP頁面可以訪問列arraylist。然後使用for循環遍歷數組列表，以便我可以創建表列。 如何將JSP頁面鏈接到servlet，以便能夠獲取所需的信息？
我必須在servlet中執行sql連接，並且不能在JSP頁面中建立連接。
好點！我確實注意到，每次我重新加載頁面時，我都會將相同的列名添加到向量中！ –