How can i apply "Factory Pattern" to instantiate Firefox, IE and Chrome Browser instances in Java

Question

so here is what i have:

Browser.java
BrowserFactory.java

ChromiumBrowser.java
InternetExlorer.java
FirefoxBrowser.java
HTMLUnitBrowser.java

SeleniumDriver.java

What i am thinking is that SeleniumDriver.java is a client of the BrowserFactory and will create an instance of a browser depending on which one is selected via a csv file :

1. ChromiumBrowser
2. InternetExlorer
3. FirefoxBrowser
4. HTMLUnitBrowser

Answer 1

You have loads of ways to implement a factory. It depends on how complex the creation and how fixed the list of entities.

The enum way:

public enum BrowserType {
    CHROME {
        public Browser create() {
            return new ChromeBrowser();
        }
    },
    IE {
        public Browser create() {
            return new IeBrowser();
        }
    }
    public abstract Browser create();
}

// Factory is optional really, the enum does the job.
public class BrowserFactor {

    public Browser create(BrowserType type) {
        return type.create();
    }
}

The map/strategy way:

interface BrowserStrategy {
    Browser create();
}

public class ChromeBrowser implements BrowserStrategy {
    public Browser create() {
        return new ChromeBrowser();
    }
}

public class BrowserFactor {
    Map<String, BrowserStrategy> ctorStategy = ...; // I'd use DI, but this could be manually created.
    public Browser create(String type) {
        return type.create();
    }
}

The map/reflection way:

public class BrowserFactor {
    Map<String, Class<? extends Browser> clazz = ...; // I'd use DI, but this could be manually created.
    public Browser create(String type) {
        return clazz.newInstance();
    }
}

My preference is to see if your DI framework can handle it for you. If not:

• Simple creation/fixed entity set - Enum or map/reflection
• Simple creation/expect the entity set will group - map/reflection
• Complex creation - map/strategy.