Java Design Pattern Rookie series (iv) Modeling and implementation of plant method model

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Factory method Mode (Factory )

Factory method: As the name implies, is called the factory method to produce objects (products).
There are 3 ways to implement factory methods:

first, the Common factory model。 is to create a factory class that creates instances of classes that implement the same interface.

1. UML Modeling Diagram:

2. Code implementation

/** * Example (i): General Factory Method *  * Disadvantage: If a string error is passed, the object cannot be created correctly */interface Sender {public void send (); Class Emailsender implements sender {@Overridepublic void send () {System.out.println ("Send with e-mail ...");}} Class Smssender implements sender {@Overridepublic void send () {System.out.println ("Send with SMS ...");}} /** * Product Factory */class sendfactory {public Sender producesender (String type) {if ("email". Equals (Type)) {return new Emailsende R ();} else if ("SMS". Equals (Type)) {return new Smssender ();} else {System.out.println ("No such type ..."); return null;}} /** * Client Test class *  * @author Leo */public class Test {public static void main (string[] args) {//create factory sendfactory Sendfacto ry = new Sendfactory ();//Sender sender = Sendfactory.producesender ("email");//shipping Sender.send ();}}

Two, multiple factory method mode。is an improvement to the common factory method pattern, in the normal factory method pattern, if the passed string is faulted, the object cannot be created correctly, and multiple factory method patterns provide multiple factory methods to create the objects individually.

1. UML Modeling Diagram:

2. Code implementation

/** * Example (b): Multiple factory methods *  * Advantages: Multiple factory method modes are provided with multiple factory methods, respectively creating the object */interface Sender {public void Send ();} Class Emailsender implements sender {@Overridepublic void send () {System.out.println ("Send with e-mail ...");}} Class Smssender implements sender {@Overridepublic void send () {System.out.println ("Send with SMS ...");}} /** * Different methods to produce the corresponding product */class sendfactory {public Sender produceemail () {return new Emailsender ();} Public Sender producesms () {return new Smssender ();}} /** * Client Test class *  * @author Leo */public class Test {public static void main (string[] args) {//create factory sendfactory Sendfacto ry = new Sendfactory ();//Production product Sender Senderemail = Sendfactory.produceemail ();//shipping Senderemail.send ();}}

third, static factory method mode。The method in the above multiple factory method pattern is set to static, do not need to create an instance, call directly.

1. UML Modeling Diagram:

2. Code implementation

/** * Example (c): Static Factory method *  * Advantages: Multiple factory method modes are provided with multiple factory methods, respectively creating the object */interface Sender {public void Send ();} Class Emailsender implements sender {@Overridepublic void send () {System.out.println ("Send with e-mail ...");}} Class Smssender implements sender {@Overridepublic void send () {System.out.println ("Send with SMS ...");}} /** * Static Factory: Different instance chemical Plant *  * Different methods to produce the corresponding product */class sendfactory {public static Sender Produceemail () {return new Emailsender ( );} public static Sender Producesms () {return new Smssender ();}} /** * Client Test class *  * @author Leo */public class Test {public static void main (string[] args) {//Direct production product Sender Senderemail = Sendfactory.produceemail ();//shipping Senderemail.send ();}}

Iv. Summary

In general, when there are a large number of products that need to be created and have a common interface, they can be created through the factory method pattern. In the above three modes, the first if the incoming string is wrong, the object is not created correctly, the third is relative to the second type, do not need to instance the chemical plant class, so, in most cases, we will choose the third- static factory method mode .

Java Design Pattern Rookie series (iv) Modeling and implementation of plant method model