在过去的三天里，我一直在尝试开发一个基于 Web 的 CRUD 应用程序来执行所有的 CRUD 操作。鉴于代码的复杂性，我决定先显示数据，然后我可以继续进行进一步的 CRUD 操作。
对于这个应用程序，我在这里发布了几个问题。从答案我走了这么远。
这是我的完整源代码。它没有显示任何错误。但我无法获得输出。
我的服务器端代码中有两个类。对我来说，它看起来不错。但它需要更多的东西才能活起来。这是一个很棒的论坛，请告诉我，我该如何克服这个问题。
1) EmpApp.java 只考虑 getAllEmployee() 方法，省略其余部分。
package test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import com.mysql.jdbc.PreparedStatement;
public abstract class EmpApp implements Set<Employee>
{
public Set<EmpApp> empobj = new HashSet<EmpApp>();
private Set<Employee> persons = new HashSet<Employee>();
public boolean add(Employee employee) {
return persons.add(employee);
}
public EmpApp(){
}
public Set<EmpApp> getAllEmp()
{
return empobj;
}
public void addEmployee(Employee employee) throws SQLException, ClassNotFoundException
{
int tempID = employee.getId();
String tname = employee.getName();
int tage = employee.getAge();
String tdept = employee.getDept();
PreparedStatement pstmt;
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/general";
Connection con = DriverManager.getConnection(url,"root", "1234");
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
pstmt = (PreparedStatement) con.prepareStatement("INSERT INTO PERSON SET ID=?, NAME=?, AGE=?, DEPT=?");
pstmt.setInt(1, tempID);
pstmt.setString(2, tname);
pstmt.setInt(3, tempID);
pstmt.setString(4, tdept);
pstmt.executeUpdate();
}
public void updateEmployee(Employee employee) throws SQLException, ClassNotFoundException
{
int tempID = employee.getId();
String tname = employee.getName();
int tage = employee.getAge();
String tdept = employee.getDept();
PreparedStatement pstmt;
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/general";
Connection con = DriverManager.getConnection(url,"root", "1234");
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
pstmt = (PreparedStatement) con.createStatement();
pstmt = (PreparedStatement) con.prepareStatement("UPDATE PERSON SET NAME=?, AGE=?, DEPT=? WHERE ID=?");
pstmt.setInt(2, tage);
pstmt.setString(1, tname);
pstmt.setString(3, tdept);
pstmt.setInt(4, tempID);
pstmt.executeUpdate();
}
public void deleteEmployee(Employee employee) throws ClassNotFoundException, SQLException
{
int eid = employee.getId();
PreparedStatement pstmt;
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/general";
Connection con = DriverManager.getConnection(url,"root", "1234");
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
pstmt = (PreparedStatement) con.createStatement();
pstmt = (PreparedStatement) con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
pstmt.executeUpdate("DELETE FROM PERSON WHERE ID="+eid);
}
@SuppressWarnings("unchecked")
private Set<EmpApp> getAllEmployee() throws ClassNotFoundException, SQLException
{
Employee employee = new Employee();
Statement stmt;
ResultSet rs;
Class.forName("com.mysql.jdbc.Driver");
String url ="jdbc:mysql://localhost:3306/general";
Connection con = DriverManager.getConnection(url,"root", "1234");
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
stmt = con.createStatement();
stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = stmt.executeQuery("SELECT * " + "from person ORDER BY ID");
while(rs.next())
{
String name = rs.getString(2);
employee.setName(name);
int id = rs.getInt(1);
employee.setId(id);
String dept = rs.getString(4);
employee.setDept(dept);
int age = rs.getInt(3);
employee.setAge(age);
empobj.addAll((Collection<? extends EmpApp>) employee);
}
return empobj;
}
}
2) 员工.java
package test;
public class Employee
{
private Set<Employee> employee = new HashSet<Employee>();
public Employee() {
// TODO Auto-generated constructor stub
}
private String name;
private String dept;
private int age;
private int id;
public int getId(){
return id;
}
public void setId(int id){
this.id = id;
}
public String getName(){
return name;
}
public void setName(String name){
this.name = Security.escapeHtml(name);;
}
public int getAge(){
return age;
}
public void setAge(int age){
this.age = age;
}
public String getDept(){
return dept;
}
public void setDept(String dept){
this.dept = Security.escapeHtml(dept);
}
public boolean equals(Object obj){
if (obj == null)
{
return false;
}
if (obj == this)
{
return true;
}
if (!this.getClass().equals(obj.getClass()))
{
return false;
}
Employee that = (Employee) obj;
if (this.id != that.id)
{
return false;
}
return true;
}
public String toString(){
return "Employee[id=" + id + ",name=" + name + "]";
}
}
index.html 代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Employee Data</title>
<script type='text/javascript' src='dwr/engine.js'> </script>
<script type='text/javascript' src='dwr/util.js'> </script>
<script type='text/javascript' src='dwr/interface/EmpApp.js'> </script>
<script>
function init() {
showTable();
}
var empCache = { };
var viewed = -1;
function showTable() {
EmpApp.getAllEmployee(function(empobj) {
dwr.util.removeAllRows("EmpRow", { filter:function(tr) {
return (tr.id != "pattern");
}});
var employee, eid;
for (var i = 0; i < empobj.length; i++) {
employee = empobj[i];
eid = empobj.id;
dwr.util.cloneNode("pattern", { idSuffix:id });
dwr.util.setValue("ID" + id, employee.id);
dwr.util.setValue("NAME" + id, employee.name);
dwr.util.setValue("AGE" + id, employee.age);
dwr.util.setValue("DEPT" + id, employee.dept);
$("pattern" + id).style.display = "table-row";
empCache[id] = employee;
}
});
}
</script>
</head>
<body onload="init();">
<div id="tabContents">
<div id="demoDiv">
<h3>Employee</h3>
<table border="1" class="rowed grey">
<thead>
<tr>
<th>ID</th>
<th>NAME</th>
<th>AGE</th>
<th>DEPT</th>
</tr>
</thead>
<tbody id="EmpRow">
<tr id="pattern" style="display:none;">
<td>
<span id="ID">Name</span><br/>
<span id="NAME">Name</span><br/>
<span id="AGE">Age</span>
</td>
<td><span id="DEPT">Dept</span></td>
</tr>
</tbody>
</table>
</div>
</body>
</html>
当然是它的异步 Web 应用程序。我在这里使用 DWR。dwr.xml 文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"
"http://getahead.org/dwr/dwr20.dtd">
<dwr>
<allow>
<create creator="new" javascript="EmpApp" scope="script">
<param name="class" value="test.EmpApp"/>
<include method="GetAllEmployee"/>
</create>
<convert match="test.EmpApp" converter="bean"/>
</allow>
</dwr>
最后的 web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>LastDisplay</display-name>
<servlet>
<servlet-name>dwr-invoker</servlet-name>
<servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>true</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>