Custom Converter in JSF is defined in three steps:
Step 1: Implement the javax.faces.convert.Converter interface to create a converter class.
Step 2: Implement the getAsString() and getAsObject() interface methods.
Step 3: To give the customized convertor a special id, use the annotation @FacesConvertor.
Creating a Custom Converter
Step 1: Create a Converter Class: UrlConverter.java
public class UrlConverter implements Converter {
...
}
Step 2: Use UrlConverter.java to implement the converter interface methods.
public class UrlData {
private String url;
public UrlData(String url) {
this.url = url;
}
...
}
public class UrlConverter implements Converter {
@Override
public Object getAsObject(FacesContext facesContext,
UIComponent component, String value) {
...
UrlData urlData = new UrlData(url.toString());
return urlData;
}
@Override
public String getAsString(FacesContext facesContext,
UIComponent component, Object value) {
return value.toString();
}
}
Step 3: Annotate to Register the Convertor: UrlConverter.java
@FacesConverter("com.codingNinjas.test.UrlConverter")
public class UrlConverter implements Converter {
}
Step 4: Utilize the JSF Page Convertor.
<h:inputText id = "urlInput" value = "#{userData.data}" label = "URL" >
<f:converter converterId = "com.codingNinjas.test.UrlConverter" />
</h:inputText>
Example:
Let's build a test JSF application to test the tag mentioned above.
Step 1: reate a project called helloworld under the package com.codingNinjas.test.
Step 2: Create UrlData.java under package com.codingNinjas.test as explained below.
Step 3: Add UrlConvertor.java as a converter to the com.codingNnijas.test package.
Step 4: Add UserData.java as a managed bean to the com.codingNinjas.test package.
Step 5: Make the changes outlined below to home.xhtml. Leave the remaining files alone.
Step 6: As stated below, create a result.xhtml in the webapps directory.
Step 7: To ensure that the business logic operates by the requirements, compile and execute the application.
Step 8: Create the programme as a war file, then deploy it to the Apache Tomcat Webserver.
Step 9: Launch your web application using the appropriate URL, as explained below in the last step.
UrlData.java
package com.codingNinjas.test;
public class UrlData {
private String url;
public UrlData(String url) {
this.url = url;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String toString() {
return url;
}
}
UrlConverter.java
package com.codingNinjas.test;
import java.net.URI;
import java.net.URISyntaxException;
import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;
import javax.faces.convert.FacesConverter;
@FacesConverter("com.codingNinjas.test.UrlConverter")
public class UrlConverter implements Converter {
@Override
public Object getAsObject(FacesContext facesContext,
UIComponent component, String value) {
StringBuilder url = new StringBuilder();
if(!value.startsWith("http://", 0)) {
url.append("http://");
}
url.append(value);
try {
new URI(url.toString());
} catch (URISyntaxException e) {
FacesMessage msg = new FacesMessage("Error converting URL",
"Invalid URL format");
msg.setSeverity(FacesMessage.SEVERITY_ERROR);
throw new ConverterException(msg);
}
UrlData urlData = new UrlData(url.toString());
return urlData;
}
@Override
public String getAsString(FacesContext facesContext,
UIComponent component, Object value) {
return value.toString();
}
}
UserData.java
package com.codingNinjas.test;
import java.io.Serializable;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
@ManagedBean(name = "userData", eager = true)
@SessionScoped
public class UserData implements Serializable {
private static final long serialVersionUID = 1L;
public UrlData data;
public UrlData getData() {
return data;
}
public void setData(UrlData data) {
this.data = data;
}
home.xhtml
<?xml version = "1.0" encoding = "UTF-8"?>
<!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"
xmlns:h = "http://java.sun.com/jsf/html"
xmlns:f = "http://java.sun.com/jsf/core">
<h:head>
<title>JSF tutorial</title>
</h:head>
<h:body>
<h2>Custom Converter Example</h2>
<h:form>
<h:inputText id = "urlInput" value = "#{userData.data}"
label = "URL" >
<f:converter converterId = "com.codingNinjas.test.UrlConverter" />
</h:inputText>
<h:commandButton value = "submit" action = "result"/>
<h:message for = "urlInput" style = "color:red" />
</h:form>
</h:body>
</html>
result.xhtml
<?xml version = "1.0" encoding = "UTF-8"?>
<!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"
xmlns:f = "http://java.sun.com/jsf/core"
xmlns:h = "http://java.sun.com/jsf/html"
xmlns:ui = "http://java.sun.com/jsf/facelets">
<h:body>
<h2>Result</h2>
<hr />
#{userData.data}
</h:body>
</html>
Let's build and execute the application after you finish all the modifications. This will result in the following outcome if everything with your application is in order.
Press the Submit button after entering an incorrect value. Observe the error notice below.
Press the Submit button after entering any legal value. View the outcome below.
Frequently Asked Questions
What does the JSF f:converter tag mean?
It is a tag for a core converter. It is used to extend the parent component with any converter.
What is the f:convertNumber tag in JSF?
It transforms user input data from components into a Java Number type. By nesting the convertNumber tag within the component tag, you may convert the data in an element to a java.lang.Number. Several characteristics are available for the convertNumber tag that let you choose the data type and format.
How does JSF relate to a bean method?
We refer to a managed bean method that performs navigation processing for the component and returns a logical outcome String.
Describe Facelets.
It is a lightweight page declaration language used to build JavaServer Faces views using HTML style.
Conclusion
Finally, you have reached the article's conclusion. Congratulations!! You gained knowledge of JSF's custom converter in this blog.
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