JSF - Custom Converter

Step No.	Description
1	Create a converter class by implementing javax.faces.convert.Converter interface.
2	Implement getAsObject() and getAsString() methods of above interface.
3	Use Annotation @FacesConvertor to assign a unique id to the custom convertor.

Step 1: Create a converter class : UrlConverter.java

public class UrlConverter implements Converter {
...
}

Step 2: Implement Converter interface methods : UrlConverter.java

Create a simple class to store data: UrlData. This class will store a URL string.

public class UrlData {

   private String url;

   public UrlData(String url){
      this.url = url;
   }
   ...
}

Use UrlData in getAsObject method.

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.tutorialspoint.test.UrlConverter")
public class UrlConverter implements Converter {
}

Use the convertor in JSF page

<h:inputText id="urlInput" value="#{userData.data}" label="URL" >
   <f:converter converterId="com.tutorialspoint.test.UrlConverter" />
</h:inputText>

Example Application

Let us create a test JSF application to test the above tag.

Step	Description
1	Create a project with a name helloworld under a package com.tutorialspoint.test as explained in the JSF - First Application chapter.
2	Create UrlData.java under package com.tutorialspoint.test as explained below.
3	Create UrlConvertor.java as a converter under package com.tutorialspoint.test as explained below.
4	Create UserData.java as a managed bean under package com.tutorialspoint.test as explained below.
5	Modify home.xhtml as explained below. Keep rest of the files unchanged.
6	Create result.xhtml in the webapps directory as explained below.
7	Compile and run the application to make sure business logic is working as per the requirements.
8	Finally, build the application in the form of war file and deploy it in Apache Tomcat Webserver.
9	Launch your web application using appropriate URL as explained below in the last step.

UrlData.java

package com.tutorialspoint.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;
   }
}

UrlConvertor.java

package com.tutorialspoint.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.tutorialspoint.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.tutorialspoint.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.tutorialspoint.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>

Once you are ready with all the changes done, let us compile and run the application as we did in JSF - First Application chapter. If everything is fine with your application, this will produce following result: