Javascript alert in JSF - jsf

Question

I have a method called bilgidorumu() in a managed bean class to check input. If there is a match with database (username and password), the application should go to the welcome page anasayfa.xhtml, else, it stays at the same page (index.xhtml). My problem is that I want to show an alert before staying on the same page (index.xhtml). So if there is no match for username/password, it should display an alert first, and stays then at index.xhtml. But I have no idea how to do that because Javascript runs on client side and Java code in server side. I have tried to display the alert with onclick event but it's not working:
<h:commandButton value="GİRİŞ" styleClass="button" action="#{kntrl.bilgidorumu()}" onclick="onBack()"/>
My input elements to reach via JS function:
<h:inputText id="username" value="#{kntrl.kulad}"
pt:placeholder="username" required="true"
requiredMessage="Kullanıcı adı girilmesi zorunlu"/> <h:inputSecret
id="pw" value="#{kntrl.kulsifre}" pt:placeholder="password"
required="true" requiredMessage="Şifre girilmesi zorunlu"/>
JS function:
function onBack(){
var kulad=document.getElementById("login-form:username").value;
var kulsifre=document.getElementById("login-form:pw").value;
alert(kulad+kulsifre);
}
index.xhtml:
<div class="login-page">
<div class="form">
<h:form class="register-form">
<h:inputText pt:placeholder="name"/>
<input type="password" placeholder="password"/>
<input type="text" placeholder="email address"/>
<button>create</button>
<p class="message">Already registered? Sign In</p>
</h:form>
<h:form class="login-form">
<h:inputText id="username" value="#{kntrl.kulad}" pt:placeholder="username" required="true" requiredMessage="Kullanıcı adı girilmesi zorunlu"/>
<h:message for="username" style="color: red"></h:message>
<h:inputSecret id="pw" value="#{kntrl.kulsifre}" pt:placeholder="password" required="true" requiredMessage="Şifre girilmesi zorunlu"/>
<h:message for="pw" style="color: red; " ></h:message>
<h:commandButton value="GİRİŞ" styleClass="button" action="#{kntrl.bilgidorumu()}" onclick="onBack()"/>
<p class="message">Not registered? Create an account</p>
</h:form>
</div>
</div>
<f:verbatim>
<script type="text/javascript">
function onBack(){
var kulad=document.getElementById("login-form:username").value;
var kulsifre=document.getElementById("login-form:pw").value;
alert(kulad+kulsifre);
}
</script>
</f:verbatim>
Managed bean:
#ManagedBean(name = "kntrl")
#RequestScoped
public class kontrolet {
private int id;
private String adsoyad;
private String birim;
private String bolum;
private String unvan;
private int puan;
private String kulad;
private String kulsifre;
public kontrolet() {
}
public String bilgidorumu() throws ScriptException {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/akademiktesvik", "root", "");
String query = "Select * from kisiler";
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(query);
while (rs.next()) {
if (rs.getString("kulad").equals(kulad) && rs.getString("kulsifre").equals(kulsifre)) {
return "anasayfa?faces-redirect=true";
}
}
} catch (Exception e) {
System.out.println("Baglanti kuurulmadı hata var" + e.getMessage());
}
return "index";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAdsoyad() {
return adsoyad;
}
public void setAdsoyad(String adsoyad) {
this.adsoyad = adsoyad;
}
public String getBirim() {
return birim;
}
public void setBirim(String birim) {
this.birim = birim;
}
public String getBolum() {
return bolum;
}
public void setBolum(String bolum) {
this.bolum = bolum;
}
public String getUnvan() {
return unvan;
}
public void setUnvan(String unvan) {
this.unvan = unvan;
}
public int getPuan() {
return puan;
}
public void setPuan(int puan) {
this.puan = puan;
}
public String getKulad() {
return kulad;
}
public void setKulad(String kulad) {
this.kulad = kulad;
}
public String getKulsifre() {
return kulsifre;
}
public void setKulsifre(String kulsifre) {
this.kulsifre = kulsifre;
}
}

Answer 1

I would not recommend to use a JavaScript alert to do so. But, if you really want to, your question would be a duplicate of:
Calling a JavaScript function from managed bean
I would suggest to simply set a message when the username and password do not match and indicate that the validation failed:
FacesContext context = FacesContext.getCurrentInstance();
FacesMessage message = new FacesMessage(FacesMessage.SEVERITY_ERROR,
"Your message",
"Message details");
context.addMessage(null, message);
context.validationFailed();
Note the null in addMessage, this means we don't set a client ID to the message. This makes the message global. To display it on your page, simply use:
<h:messages globalOnly="true"/>
See also:
How to display my application's errors in JSF?