Source code for this article: GitHub. Click here || GitEE. Click here

1. Life Scene

1. Scene description

Electrical competition is a sport that reaches the level of "competition" in a game.Intelligent antagonistic movement between people using electronic devices as sports equipment.Through competition, people's reaction ability, coordination ability and team spirit can be improved.However, different groups of people have different perspectives on competition. Some people think that competition is just addiction to the network and hold an opposing attitude, while others agree with it.The scenario is described below based on the visitor pattern.

2. Scene illustrations

3. Code implementation

public class C01_InScene {
    public static void main(String[] args) {
        DataSet dataSet = new DataSet() ;
        dataSet.addCrowd(new Youth());
        dataSet.addCrowd(new MiddleAge());
        CrowdView crowdView = new Against() ;
        dataSet.display(crowdView);
        crowdView = new Approve() ;
        dataSet.display(crowdView);
    }
}
/**
 * Double Assignment, Different Population Management
 */
abstract class Crowd {
    abstract void accept(CrowdView action);
}
class Youth extends Crowd {
    @Override
    public void accept(CrowdView view) {
        view.getYouthView(this);
    }
}
class MiddleAge extends Crowd {
    @Override
    public void accept(CrowdView view) {
        view.getMiddleAgeView (this);
    }
}
/**
 * Management of Different Population Ideas
 */
abstract class CrowdView {
    // Young people's ideas
    abstract void getYouthView (Youth youth);
    // Middle-aged Ideas
    abstract void getMiddleAgeView (MiddleAge middleAge);
}
class Approve extends CrowdView {
    @Override
    public void getYouthView(Youth youth) {
        System.out.println("Young people agree with the competition");
    }
    @Override
    public void getMiddleAgeView(MiddleAge middleAge) {
        System.out.println("Middle-aged people agree with the competition");
    }
}
class Against extends CrowdView {
    @Override
    public void getYouthView(Youth youth) {
        System.out.println("Young people oppose competition");
    }
    @Override
    public void getMiddleAgeView(MiddleAge middleAge) {
        System.out.println("Middle-aged people oppose competition");
    }
}
/**
 * Provide a data collection
 */
class DataSet {
    private List<Crowd> crowdList = new ArrayList<>();
    public void addCrowd (Crowd crowd) {
        crowdList.add(crowd);
    }
    public void display(CrowdView crowdView) {
        for(Crowd crowd : crowdList) {
            crowd.accept(crowdView);
        }
    }
}

2. Visitor Mode

1. Basic concepts

2. Pattern Diagram

3. Core Role

• Abstract Visitor Role

• Specific Visitor Role

• Abstract Node Role

• Specific Node Roles

• Structural Object Role

4. Source implementation

public class C02_Visitor {
    public static void main(String[] args) {
        ObjectStructure obs = new ObjectStructure();
        obs.add(new NodeA());
        obs.add(new NodeB());
        Visitor visitor = new VisitorA();
        obs.doAccept(visitor);
    }
}
/**
 * Abstract Visitor Role
 */
interface Visitor {
    /**
     * NodeA Access operations for
     */
    void visit(NodeA node);
    /**
     * NodeB Access operations for
     */
    void visit(NodeB node);
}
/**
 * Specific Visitor Role
 */
class VisitorA implements Visitor {
    @Override
    public void visit(NodeA node) {
        node.operationA() ;
    }
    @Override
    public void visit(NodeB node) {
        node.operationB() ;
    }
}
class VisitorB implements Visitor {
    @Override
    public void visit(NodeA node) {
        node.operationA() ;
    }
    @Override
    public void visit(NodeB node) {
        node.operationB() ;
    }
}
/**
 * Abstract Node Role
 */
abstract class Node {
    /**
     * Receive Visitors
     */
    abstract void accept(Visitor visitor);
}
/**
 * Specific Node Roles
 */
class NodeA extends Node{
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
    public void operationA(){
        System.out.println("NodeA.operationA");
    }
}
class NodeB extends Node{
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
    public void operationB(){
        System.out.println("NodeB.operationB");
    }
}
/**
 * Structural Object Role Class
 */
class ObjectStructure {
    private List<Node> nodes = new ArrayList<>();
    public void detach(Node node) {
        nodes.remove(node);
    }
    public void add(Node node){
        nodes.add(node);
    }
    public void doAccept(Visitor visitor){
        for(Node node : nodes) {
            node.accept(visitor);
        }
    }
}

3. Spring Framework Application

1. Access to Bean Structure

BeanDefinitionVisitor class, which traverses the properties of a bean; interface BeanDefinition, which defines various information about a bean, such as attribute values, construction methods, parameters, and so on.This encapsulates the relevant methods for manipulating the bean structure, but does not alter the structure of the bean.

2. Core Code Blocks

public class BeanDefinitionVisitor {
    public void visitBeanDefinition(BeanDefinition beanDefinition) {
        this.visitParentName(beanDefinition);
        this.visitBeanClassName(beanDefinition);
        this.visitFactoryBeanName(beanDefinition);
        this.visitFactoryMethodName(beanDefinition);
        this.visitScope(beanDefinition);
        if (beanDefinition.hasPropertyValues()) {
            this.visitPropertyValues(beanDefinition.getPropertyValues());
        }
        if (beanDefinition.hasConstructorArgumentValues()) {
            ConstructorArgumentValues cas = beanDefinition.getConstructorArgumentValues();
            this.visitIndexedArgumentValues(cas.getIndexedArgumentValues());
            this.visitGenericArgumentValues(cas.getGenericArgumentValues());
        }
    }
}

4. Summary of Modes

1. Advantage Description

2. Defect Description

5. Source code address

GitHub·address
https://github.com/cicadasmile/model-arithmetic-parent
GitEE·address
https://gitee.com/cicadasmile/model-arithmetic-parent