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This article mainly explains "how to use the bridging mode in java". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to use the bridge mode in java.

1. Definition of pattern

Messages are divided into ordinary messages, urgent messages, urgent messages, different message types, business function processing is not the same, now to achieve the function of sending prompt messages, how to achieve?

How can we realize the function and expand flexibly at the same time?

Definition of bridging mode:

Separate the abstract part from its implementation so that they can all change independently.

2. UML diagram

Abstraction: the interface of the abstract part, usually in this object, to maintain an object reference of the implementation part, and to abstract the methods in the object, you need to call the object of the implementation part to complete.

RefinedAbstraction: interfaces that extend abstract parts, usually in these objects, defining methods relevant to the actual business.

Implementor: the interface that defines the implementation part, usually the Implementor interface provides the basic operations, and the Abstraction defines business methods based on these basic operations

ConcreteImplementor: the object that really implements the Implementor interface

/ / the abstract part is the function corresponding to each message type, and the implementation part is the various ways to send messages / * *

* implement a unified interface for sending messages

* / public interface MessageImplementor {

/ * *

* send messages

* @ param message content of the message to be sent

* @ param toUser to whom the message is sent

, /

Public void send (String message,String toUser)

} / * *

* send messages in the form of intra-site short messages

* / public class MessageSMS implements MessageImplementor {

Public void send (String message, String toUser) {

System.out.println ("send the message'" + message+ "to" + toUser "by using the method of intra-site short message)

}

} / * *

* send messages as Email

* / public class MessageEmail implements MessageImplementor {

Public void send (String message, String toUser) {

System.out.println ("using Email, send message'" + message+ "to" + toUser ")

}

} / * *

* send messages in the form of mobile phone short messages

* / public class MessageMobile implements MessageImplementor {

Public void send (String message, String toUser) {

System.out.println ("send message'" + message+ "to" + toUser "by using SMS on mobile phone)

}

} / * *

* Abstract message object

* / public abstract class AbstractMessage {

/ * *

* hold an object in the implementation part

, /

Protected MessageImplementor impl; / * *

* Constructor, passing in the object of the implementation part

* @ param impl objects in the implementation part

, /

Public AbstractMessage (MessageImplementor impl) {this.impl = impl

} / * *

* the method of sending messages and transferring the implementation part

* @ param message content of the message to be sent

* @ param toUser to whom the message is sent

, /

Public void sendMessage (String message,String toUser) {this.impl.send (message, toUser)

}

} / * *

* ordinary messages

* / public class CommonMessage extends AbstractMessage {

Public CommonMessage (MessageImplementor impl) {super (impl)

} public void sendMessage (String message, String toUser) {/ / for ordinary messages, do nothing but call the method of the parent class directly and send the message out

Super.sendMessage (message, toUser)

}

} / * *

* urgent message

* / public class UrgencyMessage extends AbstractMessage {

Public UrgencyMessage (MessageImplementor impl) {super (impl)

} public void sendMessage (String message, String toUser) {

Message = "urgent:" + message; super.sendMessage (message, toUser)

} / * *

* monitor the processing of a message

* @ param messageId the number of the monitored message

* @ return contains the monitored data object, which is shown here, so Object is used.

, /

Public Object watch (String messageId) {/ / gets the corresponding data, organizes it into monitored data objects, and then returns

Return null

}

} / * *

* urgent news

* / public class SpecialUrgencyMessage extends AbstractMessage {

Public SpecialUrgencyMessage (MessageImplementor impl) {super (impl)

} public void hurry (String messageId) {/ / execute the urged business and send an urgent message

} public void sendMessage (String message, String toUser) {

Message = "urgent:" + message; super.sendMessage (message, toUser); / / one more message to be prompted

}

} public class Client {

Public static void main (String [] args) {/ / create specific implementation objects

MessageImplementor impl = new MessageSMS (); / / create a normal message object

AbstractMessage m = new CommonMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li"); / / create an emergency message object

M = new UrgencyMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li"); / / create an urgent message object

M = new SpecialUrgencyMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li"); / / switch the implementation to SMS, and then implement it again

Impl = new MessageMobile ()

M = new CommonMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li")

M = new UrgencyMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li")

M = new SpecialUrgencyMessage (impl)

M.sendMessage ("Please have a cup of tea", "Xiao Li")

}

}

3. Grinding design mode

1) what is bridging? Why do I need to bridge? How to bridge?

The so-called bridge, the popular point is to build a bridge between different things, so that they can be connected, can communicate with each other and use.

To bridge the separated abstract part and the implementation part, as long as the abstract part has the interface object of the implementation part, it will be bridged.

In order to achieve the goal that both the abstract part and the implementation part can be changed independently

The implementation of the abstract part usually needs to call the function of the implementation part.

2) inheritance is a common means to extend the function of an object. usually, the functional change dimension of inheritance extension is one-dimensional.

3) who will bridge:

It is who is responsible for creating the relationship between the abstract part and the implementation part, that is, who is responsible for creating the Implementor object and setting it into the object of the abstract part.

-the client is responsible for creating the Implementor, and when creating the abstract part of the object, set it to the abstract part of the object

-you can choose to create concrete Implementor objects by abstracting factories or simple factories, and classes in abstract parts can obtain Implementor objects through factory methods.

-use the IOC/DI container to create a concrete Implementor object and inject it into Abstraction

4) typical examples

JDBC: the abstract part is the API of JDBC, the concrete implementation driver

5) the essence of bridging pattern: separation of abstraction and implementation

Only by separating the abstract part from the implementation part can they change independently.

At this point, I believe you have a deeper understanding of "how to use the bridging mode in java". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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