设计模式05 建造者模式

建造者模式(Builder)定义：将一个复杂对象的构造与其表示分离，使同样的构造过程可以创建不同的表示。它将一个复杂的对象分解为多个简单对象，然后一步一步构建这个对象。所构造的对象的组成部分(数量、顺序)不变，而每一个组成部分的具体内容是可变的。

建造者模式的优点：

1、各个具体的建造者相互独立。

2、调用者不需要知道所创建的对象的内部细节。

但是使用建造这模式，必须满足所创建的对象的“各组成部分相同”，这个前提条件。

 

抽象建造者及其实现类：

public abstract class Builder {
    protected Product product = new Product();

    public abstract void buildPartA();

    public abstract void buildPartB();

    public abstract void buildPartC();

    public Product getResult() {
        return product;
    }
}

public class ConcreteBuilderA extends Builder {
    @Override
    public void buildPartA() {
        // TODO Auto-generated method stub
        product.setPartA("A->A");
    }

    @Override
    public void buildPartB() {
        // TODO Auto-generated method stub
        product.setPartB("A->B");
    }

    @Override
    public void buildPartC() {
        // TODO Auto-generated method stub
        product.setPartC("A->C");
    }
}

public class ConcreteBuilderB extends Builder {
    @Override
    public void buildPartA() {
        // TODO Auto-generated method stub
        product.setPartA("B->A");
    }

    @Override
    public void buildPartB() {
        // TODO Auto-generated method stub
        product.setPartB("B->B");
    }

    @Override
    public void buildPartC() {
        // TODO Auto-generated method stub
        product.setPartC("B->C");
    }
}

 

指挥者(对建造者发出命令的)：

public class Director {
    private Builder builder;

    public Director(Builder builder) {
        this.builder = builder;
    }
　　 //控制建造顺序
    public Product construct() { 
 9         this.builder.buildPartA();
        this.builder.buildPartB();
        this.builder.buildPartC();
        return this.builder.getResult();
    }
}

 

产品：

public class Product {
    private String partA;
    private String partB;
    private String partC;

    public void setPartA(String partA) {
        this.partA = partA;
    }

    public void setPartB(String partB) {
        this.partB = partB;
    }

    public void setPartC(String partC) {
        this.partC = partC;
    }

    public void show() {
        System.out.println(this.partA + "|" + this.partB + "|" + this.partC);
    }
}

 

调用者：

public class Client {
    /*
     * 产品都是由多个部件构成的，各个部件可以灵活选择，但其创建步骤都大同小异
     */
    public static void main(String[] args) {
        Builder builder;
        //扩展点
        builder = new ConcreteBuilderA();
        //切换到B
        //builder = new ConcreteBuilderB();
        
        //稳定代码
        Director director = new Director(builder);
        
        //创建模式，最终得到的对象
        Product product = director.construct();
        product.show();
    }
}

执行结果：

 

下面模拟一个真是场景中使用建造者模式的代码：

package com.example.uml;

//建造者模式练习
public class BuilderDemo {

    public BuilderDemo() {
        // TODO Auto-generated constructor stub
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
            
        Output output = new EnglishOutput();
        Director director = new Director(output);
        MyRecords myRecords = director.getRecord();
        System.out.println(myRecords);
    }

}

//指挥者
class Director{
    private Output output;
    
    public Director(Output output) {
        this.output = output;
    }
    
    public MyRecords getRecord() {
        return this.output.getRecord();
    }
    
}

//抽象建造者
abstract class Output{
    
    protected MyRecords myRecords = new MyRecords();
    
    public abstract void writeCourse();
    
    public abstract void writeScore();
    
    public abstract void writePasst();
    
    public MyRecords getRecord() {
        //模拟场景：先根据用户输入的课程名称，找到编号
        //根据编号查询出分数，根据分数判断是否及格
        //因此这三个方法是要按照顺序依次调用的。
        writeCourse();
        writeScore();
        writePasst();
        
        return myRecords;
    }
}

class ChineseOutput extends Output{
    @Override
    public void writeCourse() {
        // TODO Auto-generated method stub
        myRecords.setCourse("语文");
    }

    @Override
    public void writeScore() {
        // TODO Auto-generated method stub
        myRecords.setScore(80);
    }

    @Override
    public void writePasst() {
        // TODO Auto-generated method stub
        myRecords.setPass(true);
    }
}


class EnglishOutput extends Output{
    @Override
    public void writeCourse() {
        // TODO Auto-generated method stub
        myRecords.setCourse("英语");
    }

    @Override
    public void writeScore() {
        // TODO Auto-generated method stub
        myRecords.setScore(55);
    }

    @Override
    public void writePasst() {
        // TODO Auto-generated method stub
        myRecords.setPass(false);
    }
}

//模型类，成绩表
class MyRecords{
    //课程名称
    private String Course;
    
    //分数
    private Integer Score;
    
    //是否及格
    private Boolean Pass;

    public Boolean getPass() {
        return Pass;
    }

    public void setPass(Boolean pass) {
        Pass = pass;
    }

    public String getCourse() {
        return Course;
    }

    public void setCourse(String course) {
        Course = course;
    }

    public Integer getScore() {
        return Score;
    }

    public void setScore(Integer score) {
        Score = score;
    }

    @Override
    public String toString() {
        return "MyRecords [Course=" + Course + ", Score=" + Score + ", Pass=" + Pass + "]";
    }    
}