编辑：当显示帐户视图时，我无法让数据库从我正在进行的迷你银行帐户项目中提取acctNo，Cust Id，帐户类型和余额。我在那里添加了帐户业务对象以确保SQL连接到拉起，名称拉起但是acctNo，Cust Id，帐户类型和余额不会。它全部连接在一起，因此我将它们全部添加，所有页面都可以工作，但没有任何内容从数据库中弹出
如何连接此servlet：
@WebServlet(urlPatterns = {"/AccountLookupServlet"})
public class AccountLookupServlet extends HttpServlet {
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 id = request.getParameter("id");
String pw = request.getParameter("pw");
System.out.println(id);
System.out.println(pw);
Account a1=new Account();
a1.findDB(id);
String an=a1.getAcctNo();
System.out.println(an);
String ln=a1.getCustId();
System.out.println(ln);
String at=a1.getType();
System.out.println(at);
double bal=a1.getBalance();
System.out.println(bal);
HttpSession ses1=request.getSession();
ses1.setAttribute("a1", a1);
}
}
/**
* Handles the HTTP <code>GET</code> method.
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request,response);
}
/**
* Handles the HTTP <code>POST</code> method.
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String action = request.getParameter("action");
if (action.equals(null)) {
request.getRequestDispatcher("/index.jsp").forward(request, response);
}
/* Gets single searched account from the accountLookup.jsp */
else if (action.equals("getAcct")) {
String acctNo = request.getParameter("accountNo");
try {
/* Instantiates a new Account class and sets it as a request attribute
for use in the accountView.jsp */
Account account = new Account(acctNo);
request.setAttribute("account", account);
request.getRequestDispatcher("/accountView.jsp").forward(request, response);
} catch (SQLException ex) {
Logger.getLogger(AccountLookupServlet.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}
}
要连接到此jsp页面以提取出现在我创建的表格中的客户ID，帐号，帐户类型和余额？ Servlet正在工作，数据库已连接，我只需要一种方法让JSP页面读入数据并实际打印出来。
<%@page import="Business.Account"%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Your Account</title>
<link rel="stylesheet" href="chattBank.css" type="text/css">
<style>
#image{
text-align: center;
}
#acctForm{
text-align: center;
}
#acctTable{
margin-left: 645px;
}
#submitTable{
margin-left: 755px;
}
table{
margin-left: auto;
margin-right: auto;
}
h4{
text-align: center;
}
</style>
</head>
<body>
<div id = "image">
<img src="bankpic.jpg" />
</div>
<h4>Here Is The Account You Requested</h4>
<table border="1" width="75%" cellspacing="5" cellpadding="2">
<thead>
<tr>
<th colspan="10">Your Chatt Accounts</th>
</tr>
</thead>
<tbody>
<tr>
<td colspan="2"></td>
<td colspan="2">Customer Id</td>
<td colspan="2">Account Number</td>
<td colspan="2">Account Type</td>
<td colspan="2">Account Balance</td>
</tr>
<tr>
<td colspan="2">Account: </td>
<td colspan="2">${account.custId}</td>
<td colspan="2">${account.acctNo}</td>
<td colspan="2">${account.type}</td>
<td colspan="2">${account.balance}</td>
</tr>
</tbody>
</table>
<table width="50%" cellspacing="5" cellpadding="2">
<thead>
<tr>
<td></td>
<td>Click Here To Navigate To A New Page</td>
<td></td>
</tr>
</thead>
<tbody>
<tr>
<td><a href="AccountServlet?action=view&id=${customer.custId}">View All Accounts</a></td>
<td><a href="ManageAccounts?action=manage&id=${customer.custId}">Manage Accounts</a></td>
<td><a href="Logout?action=logout">Log Out</a></td>
</tr>
</tbody>
</table>
</body>
</html>
以下是帐户业务对象：要确保连接到accountview.jsp以连接到帐户以提取帐户信息的数据库是正确的。
公共类帐户实现Serializable {
private String acctNo;
private String custId;
private String type;
private double balance;
private String message;
/**
* No-Arg Constructor
*/
public Account() {
}
/**
* Single Arg constructor accepts one parameter
* connects to database and builds the customers
* account object
* @param acct
*/
public Account(String acct) throws SQLException {
Connection connect = null;
Statement statement = null;
ResultSet result = null;
String sql = "SELECT * FROM Accounts WHERE acctNo = '" + acct + "';";
try {
/*establishes connection and creates statement */
connect = acctConnect();
statement = connect.createStatement();
result = statement.executeQuery(sql);
/*loops through the database row containing the information
and builds the row*/
while (result.next()) {
this.acctNo = result.getString("acctNo");
this.custId = result.getString("Cid");
this.type = result.getString("Type");
this.balance = result.getDouble("Balance");
}
} catch (SQLException e) {
System.out.println("Error: " + e);
} finally {
connect.close();
}
}
/**
*sets account number
*@param acctNo
*/
public void setAcctNo(String acctNo) {
this.acctNo = acctNo;
}
/**
*sets customer id
* @param custId
*/
public void setCustId(String custId) {
this.custId = custId;
}
/**
* sets account type
* @param acctType
*/
public void type(String type) {
this.type = type;
}
/**
* sets balance for the account
* @param balance
*/
public void setBalance(double balance) {
this.balance = balance;
}
/**
* returns account number
* @return String
*/
public String getAcctNo() {
return acctNo;
}
/**
* returns customer id
* @return String
*/
public String getCustId() {
return custId;
}
/**
* returns account type
* @return String
*/
public String getType() {
return type;
}
/**
* returns account balance
* @return double
*/
public double getBalance() {
return balance;
}
/**
* returns account information into string form
* @return String
*/
public String getAcct() {
return this.acctNo + " " + this.custId + " " + this.type + " " + this.balance;
}
/**
* returns message set by other methods in class
* @return String
*/
public String getMessage(){
return this.message;
};
/**
* Establishes connection to database
* @return Connection
*/
public static Connection acctConnect() {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch (ClassNotFoundException e) {
System.out.println("Errors: " + e);
}
/*Declare new connection*/
Connection con = null;
try {
/*Define connection*/
con = DriverManager.getConnection("jdbc:odbc:ChattDB");
} catch (SQLException e) {
System.out.println("Error: " + e);
}
/*Returns connection con*/
return con;
}
/**
* Uses object account number to get all information from the database
* where the account number is valid
*/
public void findDB() {
Connection connect = null;
Statement statement = null;
ResultSet result = null;
String sql = "SELECT * FROM Accounts WHERE acctNo = '" + acctNo + "';";
try {
connect = acctConnect();
statement = connect.createStatement();
result = statement.executeQuery(sql);
/*Loop through the result to gather all of the information from the
row in the database*/
while (result.next()) {
this.acctNo = result.getString("acctNo");
this.custId = result.getString("Cid");
this.type = result.getString("Type");
this.balance = result.getDouble("Balance");
}
connect.close();
} catch (SQLException e) {
System.out.println("Error: " + e);
}
}
/**
* Connects to the database accesses the desired account and deposits to that
* account. Updates the database. and finally closes the connection. This
* method throws the sql exception.
* @param acctNo
* @param depAmount
* @throws SQLException
*/
public void deposit(String acctNo, double depAmount) throws SQLException {
Connection connect = acctConnect();
Statement statement = connect.createStatement();
ResultSet result = null;
String sql = "Select balance From Accounts Where acctNO = '" + acctNo + "';";
String update = null;
int updateSet = 0;
double balance = 0.00;
double newBalance;
result = statement.executeQuery(sql);
/* retrieves the balance of the current account */
while (result.next()) {
balance = result.getDouble("Balance");
}
/* updates the balance in this object and the database */
newBalance = balance + depAmount;
update = "Update Accounts Set Balance = '" + newBalance + "' Where acctNO = '" + acctNo + "';";
updateSet = statement.executeUpdate(update);
this.balance = newBalance;
/* closes connection */
connect.close();
}
/**
* Withdraws funds from the current account. Throws an exception
* for insufficient funds
* @param acctNo
* @param withdrawal
* @throws SQLException
* @throws Exception
*/
public void withdraw(String acctNo, double withdrawal) throws SQLException, Exception {
Connection connect = acctConnect();
Statement statement = connect.createStatement();
ResultSet result = null;
String sql = "Select balance From Accounts Where acctNO = '" + acctNo + "';";
String update = null;
int updateSet = 0;
double balance = 0.00;
double newBalance;
result = statement.executeQuery(sql);
/* gets balance of the current account from the database */
while (result.next()) {
balance = result.getDouble("Balance");
}
/* checks to see if the withdrawal amount is more than the balance
and if so the exception is thrown and an insufficient funds message is
set */
if (balance < withdrawal){
this.message = "Insufficcient Funds";
throw new Exception();
}else{
/* sets new balance and updates the current database account balance */
newBalance = balance - withdrawal;
update = "Update Accounts Set Balance = '" + newBalance + "' Where acctNo = '" + acctNo + "';";
updateSet = statement.executeUpdate(update);
this.balance = newBalance;
}
/* closes connection to database */
connect.close();
}
/**
* Transfers funds from one account to another by calling the withdrawal
* and deposit methods.
* @param fromAcct
* @param toAcct
* @param transfer
* @throws SQLException
* @throws Exception
*/
public void transfer(String fromAcct, String toAcct, double transfer) throws SQLException, Exception {
/* Call withdraw method on from account */
withdraw(fromAcct, transfer);
/* deposit to to account */
deposit(toAcct, transfer);
/* both methods close their own database connection so it is not necessary to do so here */
}
/**
* Sets up new account for existing customers
* @param acctNo
* @param custID
* @param type
* @param balance
* @throws SQLException
*/
public void estabAccount(String custID, String type, double balance) throws SQLException {
System.out.println(custID + " " + type + " " + balance);
/* Establish connection and update the database with a new row containing the new account info */
Connection connect = acctConnect();
Statement statement = connect.createStatement();
String sql = "Insert Into accounts (Cid, Type, Balance) Values ('" + custID + "', '" + type + "', " + balance + ");";
System.out.println(sql);
/* Execute Query and close connection */
statement.executeUpdate(sql);
connect.close();
}
public void findDB(String id) {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
}
}
答案 0 :(得分：0)
看看你的EL片刻，你有这些线路：
<td colspan="2">${account.custId}</td>
<td colspan="2">${account.acctNo}</td>
<td colspan="2">${account.type}</td>
<td colspan="2">${account.balance}</td>
您说要访问名为balance的变量的account字段，这是完全有效的，但是，在您的servlet中，您将帐户变量分配给名为{的会话属性{1}} 不 a1，因此EL不知道该放什么
TL; DR将您的account更改为ses1.setAttribute("a1", a1);
有关表达式语言（EL）see this
的更多信息