接著昨天https://www.aiwalls.com/kf/201203/124792.html 的寫，實現登錄的服務端部分。首先得弄個數據庫，然後建立一個表，存儲所有用戶的用戶名和密碼，當在客戶端發出查詢請求的時候會把用戶輸入的用戶名和密碼傳到服務器端，然後在數據庫中進行查詢，這裡我們的表就3個字段，一個ID，一個username和一個password。
然後就是編碼實現瞭，首先是寫一個類封裝一下數據庫中的用戶信息，如下：
[java] public class User {
private int id;
private String username;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return username;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
public class User {
private int id;
private String username;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return username;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
} 然後就是定義查詢的接口：
[java] public interface UserDao {
// 登錄方法
public User login(String username,String password);
}
public interface UserDao {
// 登錄方法
public User login(String username,String password);
} 實現該接口：
[java] public class UserDaoImpl implements UserDao {
public User login(String account, String password) {
// 查詢SQL語句
String querySql = " select id,username,password "+
" from userTable "+
" where username=? and password=? ";
DBUtil util = new DBUtil();
Connection conn = util.openConnection();
try {
PreparedStatement state = conn.prepareStatement(querySql);
state.setString(1, username);
state.setString(2, password);
ResultSet result = state.executeQuery();
if (result.next()) {
int id = result.getInt(1);
String name = result.getString(4);
User user = new User();
user.setId(id);
user.setName(username);
user.setPassword(password);
return user;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
util.closeConn(conn);
}
return null;
}
}
public class UserDaoImpl implements UserDao {
public User login(String account, String password) {
// 查詢SQL語句www.aiwalls.com
String querySql = " select id,username,password "+
" from userTable "+
" where username=? and password=? ";
DBUtil util = new DBUtil();
Connection conn = util.openConnection();
try {
PreparedStatement state = conn.prepareStatement(querySql);
state.setString(1, username);
state.setString(2, password);
ResultSet result = state.executeQuery();
if (result.next()) {
int id = result.getInt(1);
String name = result.getString(4);
User user = new User();
user.setId(id);
user.setName(username);
user.setPassword(password);
return user;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
util.closeConn(conn);
}
return null;
}
} 最後就是實現servlet，主要是處理來自客戶端的查詢請求和返回查詢結果：
[java] public class Login extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
UserDao dao = new UserDaoImpl();
// 獲得客戶端請求參數
String username = request.getParameter("username");
String password = request.getParameter("password");
User u = dao.login(username, password);
if(u!=null){
out.print("登錄成功");
}else{
out.print("null");
}
out.flush();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
public void init() throws ServletException {
}
public LoginServlet() {
super();
}
public void destroy() {
super.destroy();
}
}
public class Login extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
UserDao dao = new UserDaoImpl();
// 獲得客戶端請求參數
String username = request.getParameter("username");
String password = request.getParameter("password");
User u = dao.login(username, password);
if(u!=null){
out.print("登錄成功");
}else{
out.print("null");
}
out.flush();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}
public void init() throws ServletException {
}
public LoginServlet() {
super();
}
public void destroy() {
super.destroy();
}
} 至於Tomcat和MySQL的配置、使用網上有不少教程！至此就可以實現登錄模塊瞭！
摘自 chenlong12580的專欄
