我是java的新手，我尝试使用servlet更新文本字段。插入和删除已完成，但更新无效。我只是使用HTML和servlet。 这是我的servlet
ComputerController.java
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
ComputerDAO comDAO = new ComputerDAO();
//get Service
String service = request.getParameter("service");
if (service == null || service == "") {
service = "listAllComputer";
}
if (service.equals("addComputer")) {
//get parameter
String name = request.getParameter("cname");
String quan = request.getParameter("quantity");
String price = request.getParameter("price");
String func = request.getParameter("functions");
//Check invalid here
Computer com = new Computer(0, name, Integer.parseInt(quan), Double.parseDouble(price), func);
//add into DB
int n = comDAO.addComputer(com);
if (n > 0) {
out.println("<h1> INSERTED</h1>");
}
}
if (service.equalsIgnoreCase("listallcomputer")) {
ArrayList<Computer> arr = comDAO.getAllComputer("select * from Computer");
if (arr.size() == 0) {
out.println("<h1> NO RECORD FOUND </h1>");
} else {
out.println(" <table width='100%' border='1'>");
out.println("<caption>");
out.println(" <h2>Computer List</h2>");
out.println(" </caption>");
out.println("<tr>");
out.println(" <th scope='col' width='5%'>id</th>");
out.println(" <th scope='col'width='30%'>Computer Name</th>");
out.println(" <th scope='col'width='10%'>Quantity</th>");
out.println(" <th scope='col'width='15%'>Price</th>");
out.println(" <th scope='col'width='30%'>Functions</th>");
out.println(" <th scope='col' colspan=2 width='10%'>Action</th>");
out.println(" </tr>");
for (int i = 0; i < arr.size(); i++) {
Computer com = arr.get(i);
out.println("<tr>");
out.println(" <td>" + com.getCid() + "</td>");
out.println(" <td>" + com.getCname() + "</td>");
out.println(" <td>" + com.getQuantity() + "</td>");
out.println(" <td>" + com.getPrice() + "</td>");
out.println(" <td>" + com.getFunc() + "</td>");
out.println(" <td><a href = ComputerController?service=update&id=" + com.getCid() + ">Update</a></td>");
out.println(" <td><a onclick= \"return confirm('Are you sure you want to delete this item?');\" href=ComputerController?service=delete&id=" + com.getCid() + ">Delete</a></td>");
out.println(" </tr>");
}
out.println("</table>");
out.println("<a href= index.jsp>Back to Main page</a>");
}
}
if (service.equalsIgnoreCase("delete")) {
String deleteId = request.getParameter("id");
try {
if (deleteId != null) {
int deleteIdInt = Integer.parseInt(deleteId);
int isOk = comDAO.removeComputer(deleteIdInt);
if (isOk != 0) {
out.print("Deleted computer with id = " + deleteIdInt);
} else {
out.print("Error");
}
}
} catch (Exception ex) {
out.print(ex.getMessage());
}
}
if (service.equalsIgnoreCase("update")) {
out.println(" <html>");
out.println("<body>");
out.println("<form id='form1' name='form1' method='post' action='ComputerController' style='width: 500px; margin: 20px auto 0 auto;'>");
out.println("<h2>Update Computer</h2>");
out.println(" <table width='100%' border='0'>");
out.println("<tr>");
out.println(" <th width='28%' scope='row'>Computer Name</th>");
out.println(" <td width='72%'><input type='text' name='cnameUpdate' id='cnameUpdate' /></td>");
out.println(" </tr>");
out.println(" <tr>");
out.println(" <th scope='row'>Quantity</th>");
out.println(" <td><input type='text' name='quanUpdate' id='quanUpdate' /></td>");
out.println("</tr>");
out.println("<tr>");
out.println(" <th scope='row'>Price</th>");
out.println(" <td><input type='text' name='priceUpdate' id='priceUpdate' /></td>");
out.println("</tr>");
out.println("<tr>");
out.println(" <th scope='row'>Functions</th>");
out.println(" <td><textarea rows='4' name='funcUpdate' id='funcUpdate'></textarea></td>");
out.println(" </tr>");
out.println("<tr>");
out.println(" <th scope='row'> </th>");
out.println(" <td><input type='submit' name='button' id='button' value='Update' />");
out.println(" <input name='updateComputer' type='hidden' id='updateComputer' value='updateComputer' /></td>");
out.println(" </tr>");
out.println(" </table>");
out.println(" </form>");
out.println(" </body>");
out.println("</html>");
}
if (service.equalsIgnoreCase("updateComputer")) {
String uid = request.getParameter("cid");
String uname = request.getParameter("cname");
String uquan = request.getParameter("quantity");
String uprice = request.getParameter("price");
String ufunc = request.getParameter("functions");
Computer com = new Computer(Integer.parseInt(uid), uname, Integer.parseInt(uquan), Double.parseDouble(uprice), ufunc);
int n = comDAO.updateComputer(com);
if (n > 0) {
out.print("<h2>Updated</h2>");
}
}
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
这是我的DAO。我认为该文件中没有问题
ComputerDAO.java
public int addComputer(Computer com) {
int n = 0;
try {
Statement add = conn.createStatement();
String sql = "INSERT INTO Computer(cname,quantity,price,functions)" + "values(?,?,?,?)";
PreparedStatement pre = conn.prepareStatement(sql);
pre.setString(1, com.getCname());
pre.setInt(2, com.getQuantity());
pre.setDouble(3, com.getPrice());
pre.setString(4, com.getFunc());
n = pre.executeUpdate();
} catch (SQLException ex) {
Logger.getLogger(ComputerDAO.class.getName()).log(Level.SEVERE, null, ex);
}
return n;
}
public ResultSet getData(String sql) {
try {
state = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
rs = state.executeQuery(sql);
} catch (SQLException ex) {
Logger.getLogger(ComputerDAO.class.getName()).log(Level.SEVERE, null, ex);
}
return rs;
}
public ArrayList<Computer> getAllComputer(String sql) {
ArrayList<Computer> arr = new ArrayList<Computer>();
try {
state = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
rs = state.executeQuery(sql);
while (rs.next()) {
int id = rs.getInt("cid");
String cname = rs.getString(2);
int quan = rs.getInt(3);
double price = rs.getDouble(4);
String func = rs.getString(5);
Computer com = new Computer(id, cname, quan, price, func);
arr.add(com);
}
} catch (SQLException ex) {
Logger.getLogger(ComputerDAO.class.getName()).log(Level.SEVERE, null, ex);
}
return arr;
}
public int removeComputer(int id) {
int n = 0;
try {
//code here
String query = "DELETE FROM Computer WHERE cid = '" + id + "'";
Statement st = conn.createStatement();
int rs = st.executeUpdate(query);
return rs;
} catch (SQLException ex) {
Logger.getLogger(ComputerDAO.class.getName()).log(Level.SEVERE, null, ex);
}
return n;
}
public int updateComputer(Computer com) {
int n = 0;
try {
//code here
String query = "UPDATE Computer SET cname ='" + com.getCname() + "', quantity = " + com.getQuantity() + ", price = '" + com.getPrice() + ", functions = '" + com.getFunc() + "' WHERE cid = " + com.getCid() + "";
Statement st = conn.createStatement();
int rs = st.executeUpdate(query);
return rs;
} catch (SQLException ex) {
System.out.println(ex.getMessage());
Logger.getLogger(ComputerDAO.class.getName()).log(Level.SEVERE, null, ex);
}
return n;
}
答案 0 :(得分：0)
您可以在写入更新页面时设置所有控制器的值。像这样：
out.println("<input name='updateComputer' type='hidden' id='updateComputer' value='"+compId+"'/></td>");
在上面代码中的value='"+compId+"'"处留言。我在代码中的任何地方都没有看到您在表单上设置值。除非我遗失了什么。