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我有兩個文件，一個是前端login.jsp和後端loginUser.java。我正在嘗試從loginUser.java獲得boolean。但是，出現了一個錯誤java.lang.IncompatibleClassChangeError。我不知道爲什麼這會出現。我怎樣才能解決這個錯誤？謝謝。如何解決 - java.lang.IncompatibleClassChangeError？
這裏是我的 '的login.jsp' 的代碼：
try{
out.println("HT");
login.LoginUser user = new login.LoginUser(id,pwd);
boolean login_success = user.isLogin(); <---This line have error.
//int role_id = user.get_role_id();
if (login_success){
out.println("Login Success");
// out.println(user.get_role_id().toString());
%>
<script>
setTimeout(function() {
window.location.href = "control_panel.jsp"; //will redirect to your blog page (an ex: blog.html)
},2000);
</script>
<%
}
else{
out.println("Login Failed");
%>
這裏是我的 'loginUser.java' 的代碼：
public class LoginUser {
private String username,password;
public boolean login_success;
public int role_id;
public LoginUser(String username,String password){
this.username=username;
this.password=password;
this.login_success=false;
this.role_id = 0;
}
public boolean login(){
db.DataConnect conn = new db.DataConnect();
conn.connect();
ResultSet login_result;
String sql_statement = "SELECT COUNT(*) AS user_found, role_id FROM t_user WHERE user_name = '" + this.username + "' AND password = '" + this.password + "'";
System.out.println(sql_statement);
try{
login_result = conn.select(sql_statement);
if(login_result.next()){
if(login_result.getInt("user_found") == 1){
login_success = true;
role_id = login_result.getInt("role_id");
}
}
} catch (Exception e) {System.out.println(e);}
conn.close();
return login_success;
}
public boolean isLogin(){
return true;
}
}
然而，當我改了行boolean login_success = user.isLogin();到boolean login_success = user.login();，錯誤不會出來。