设计模式之建造者模式

• 模式定义

将一个复杂对象的创建与他的表示分离，使得同样的构建过程可以创建不同的表示

• 应用场景

1.需要生成的对象具有复杂的内部结构
2.需要生成的对象内部属性本身相互依赖
3.与不可变对象配合使用

• 优点

1、建造者独立，易扩展。
2、便于控制细节风险。

示例：

public class BuilderTest {
    public static void main(String[] args) {

    }
}

interface ProductBuilder{
    void builderProductName(String productName);
    void builderCompanyName(String companyName);
    void builderPart1(String part1);
    void builderPart2(String part2);
    void builderPart3(String part3);
    void builderPart4(String part4);

    Product build();
}

class DefaultConcreateProductBuilder implements ProductBuilder{
    private String productName;
    private String companyName;
    private String part1;
    private String part2;
    private String part3;
    private String part4;
    @Override
    public void builderProductName(String productName) {
        this.productName=productName;
    }

    @Override
    public void builderCompanyName(String companyName) {
        this.companyName=companyName;
    }

    @Override
    public void builderPart1(String part1) {
        this.part1=part1;
    }

    @Override
    public void builderPart2(String part2) {
        this.part2=part2;
    }

    @Override
    public void builderPart3(String part3) {
        this.part3=part3;
    }

    @Override
    public void builderPart4(String part4) {
        this.part4=part4;
    }

    @Override
    public Product build() {
        return new Product(this.productName,this.companyName,this.part1,this.part2,this.part3,this.part4);
    }
}

class Director{
    private ProductBuilder builder;

    public Director(){
        this.builder=builder;
    }

    public Product makeProduct(String productName,String companyName,String part1,
                               String part2, String part3,String part4){
        builder.builderProductName(productName);
        builder.builderCompanyName(companyName);
        builder.builderPart1(part1);
        builder.builderPart2(part2);
        builder.builderPart3(part3);
        builder.builderPart4(part4);

        Product product = builder.build();
        return product;
    }
}

class Product{
    private String productName;
    private String companyName;
    private String part1;
    private String part2;
    private String part3;
    private String part4;

    public Product(){

    }

    public Product(String productName, String companyName, String part1, String part2, String part3, String part4) {
        this.productName = productName;
        this.companyName = companyName;
        this.part1 = part1;
        this.part2 = part2;
        this.part3 = part3;
        this.part4 = part4;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    public String getPart1() {
        return part1;
    }

    public void setPart1(String part1) {
        this.part1 = part1;
    }

    public String getPart2() {
        return part2;
    }

    public void setPart2(String part2) {
        this.part2 = part2;
    }

    public String getPart3() {
        return part3;
    }

    public void setPart3(String part3) {
        this.part3 = part3;
    }

    public String getPart4() {
        return part4;
    }

    public void setPart4(String part4) {
        this.part4 = part4;
    }

    @Override
    public String toString() {
        return "Product{" +
                "productName='" + productName + ''' +
                ", companyName='" + companyName + ''' +
                ", part1='" + part1 + ''' +
                ", part2='" + part2 + ''' +
                ", part3='" + part3 + ''' +
                ", part4='" + part4 + ''' +
                '}';
    }
}

• 更多的是与不可变对象结合使用

public class BuilderTest2 {
    public static void main(String[] args) {
        Product.Builder builder = new Product.Builder().productName("yang").companyName("long").part1("xx");
        builder.part3("oo");
        Product product = builder.build();
        System.out.println(product);
    }
}

class Product {
    private final String productName;
    private final String companyName;
    private final String part1;
    private final String part2;
    private final String part3;
    private final String part4;


    public Product(String productName, String companyName, String part1, String part2, String part3, String part4) {
        this.productName = productName;
        this.companyName = companyName;
        this.part1 = part1;
        this.part2 = part2;
        this.part3 = part3;
        this.part4 = part4;
    }

    static class Builder {
        private String productName;
        private String companyName;
        private String part1;
        private String part2;
        private String part3;
        private String part4;

        public Builder productName(String productName){
            this.productName=productName;
            return this;
        }
        public Builder companyName(String companyName){
            this.companyName=companyName;
            return this;
        }
        public Builder part1(String part1){
            this.part1=part1;
            return this;
        }
        public Builder part2(String part2){
            this.part2=part2;
            return this;
        }
        public Builder part3(String part3){
            this.part3=part3;
            return this;
        }
        public Builder part4(String part4){
            this.part4=part4;
            return this;
        }

        Product build(){
            return new Product(this.productName,this.companyName,this.part1,this.part2,this.part3,this.part4);
        }
    }

    @Override
    public String toString() {
        return "Product{" +
                "productName='" + productName + ''' +
                ", companyName='" + companyName + ''' +
                ", part1='" + part1 + ''' +
                ", part2='" + part2 + ''' +
                ", part3='" + part3 + ''' +
                ", part4='" + part4 + ''' +
                '}';
    }
}

• Spring源码中的应用

org.springframework.web.servlet.mvc.method.RequestMappingInfo
org.springframework.beans.factory.support.BeanDefinitionBuilder