1. 定义

将一个复杂对象的创建与它的表示分离，使得同样的构建过程可以创建不同的表示。

2. 实现

2.1 Product

  1. class Product {
  2.     private String productName;
  3.     private String companyName;
  4.     private String part1;
  5.     private String part2;
  6.     private String part3;
  7.     private String part4;
  9.     public Product() {
  10.     }
  12.     public Product(String productName, String companyName, String part1, String part2, String part3, String part4) {
  13.         this.productName = productName;
  14.         this.companyName = companyName;
  15.         this.part1 = part1;
  16.         this.part2 = part2;
  17.         this.part3 = part3;
  18.         this.part4 = part4;
  19.     }
  21.     public String getProductName() {
  22.         return productName;
  23.     }
  25.     public void setProductName(String productName) {
  26.         this.productName = productName;
  27.     }
  29.     public String getCompanyName() {
  30.         return companyName;
  31.     }
  33.     public void setCompanyName(String companyName) {
  34.         this.companyName = companyName;
  35.     }
  37.     public String getPart1() {
  38.         return part1;
  39.     }
  41.     public void setPart1(String part1) {
  42.         this.part1 = part1;
  43.     }
  45.     public String getPart2() {
  46.         return part2;
  47.     }
  49.     public void setPart2(String part2) {
  50.         this.part2 = part2;
  51.     }
  53.     public String getPart3() {
  54.         return part3;
  55.     }
  57.     public void setPart3(String part3) {
  58.         this.part3 = part3;
  59.     }
  61.     public String getPart4() {
  62.         return part4;
  63.     }
  65.     public void setPart4(String part4) {
  66.         this.part4 = part4;
  67.     }
  68. }

2.2 ProductBuilder

  1. interface ProductBuilder {
  2.     void builderProductName(String productName);
  4.     void builderCompanyName(String companyName);
  6.     void builderPart1(String part1);
  8.     void builderPart2(String part2);
  10.     void builderPart3(String part3);
  12.     void builderPart4(String part4);
  14.     Product build();
  15. }

2.3 DefaultConcreteProductBuilder

  1. class DefaultConcreteProductBuilder implements ProductBuilder {
  2.     private String productName;
  3.     private String companyName;
  4.     private String part1;
  5.     private String part2;
  6.     private String part3;
  7.     private String part4;
  9.     @Override
  10.     public void builderProductName(String productName) {
  11.         this.productName = productName;
  12.     }
  14.     @Override
  15.     public void builderCompanyName(String companyName) {
  16.         this.companyName = companyName;
  17.     }
  19.     @Override
  20.     public void builderPart1(String part1) {
  21.         this.part1 = part1;
  22.     }
  24.     @Override
  25.     public void builderPart2(String part2) {
  26.         this.part2 = part2;
  27.     }
  29.     @Override
  30.     public void builderPart3(String part3) {
  31.         this.part3 = part3;
  32.     }
  34.     @Override
  35.     public void builderPart4(String part4) {
  36.         this.part4 = part4;
  37.     }
  39.     @Override
  40.     public Product build() {
  41.         return new Product(this.productName, this.companyName, this.part1, this.part2, this.part3, this.part4);
  42.     }
  43. }

2.4 SpecialConcreteProductBuilder

  1. class SpecialConcreteProductBuilder implements ProductBuilder {
  2.     private String productName;
  3.     private String companyName;
  4.     private String part1;
  5.     private String part2;
  6.     private String part3;
  7.     private String part4;
  9.     @Override
  10.     public void builderProductName(String productName) {
  11.         this.productName = productName;
  12.     }
  14.     @Override
  15.     public void builderCompanyName(String companyName) {
  16.         this.companyName = companyName;
  17.     }
  19.     @Override
  20.     public void builderPart1(String part1) {
  21.         this.part1 = part1;
  22.     }
  24.     @Override
  25.     public void builderPart2(String part2) {
  26.         this.part2 = part2;
  27.     }
  29.     @Override
  30.     public void builderPart3(String part3) {
  31.         this.part3 = part3;
  32.     }
  34.     @Override
  35.     public void builderPart4(String part4) {
  36.         this.part4 = part4;
  37.     }
  39.     @Override
  40.     public Product build() {
  41.         return new Product(this.productName, this.companyName, this.part1, this.part2, this.part3, this.part4);
  42.     }
  43. }

2.5 Director

  1. class Director {
  2.     private ProductBuilder builder;
  4.     public Director(ProductBuilder builder) {
  5.         this.builder = builder;
  6.     }
  8.     public Product makeProduct(String productName, String companyName, String part1, String part2, String part3, String part4) {
  9.         builder.builderProductName(productName);
  10.         builder.builderCompanyName(companyName);
  11.         builder.builderPart1(part1);
  12.         builder.builderPart2(part2);
  13.         builder.builderPart3(part3);
  14.         builder.builderPart4(part4);
  15.         Product product = builder.build();
  16.         return product;
  17.     }
  18. }

2.6 使用

  1.  public static void main(String[] args) {
  2.         SpecialConcreteProductBuilder specialConcreteProductBuilder = new SpecialConcreteProductBuilder();
  3.         Director director = new Director(specialConcreteProductBuilder);
  4.         Product product = director.makeProduct("productName1", "com...", "part1", "part2", "part3", "part4");
  5.         System.out.println(product);
  6.     }

3. 建造者模式与不可变对象配合使用

3.1 Product

  1. /不可变对象，属性定义为final
  2. class Product {
  4.     private final String productName;
  5.     private final String companyName;
  6.     private final String part1;
  7.     private final String part2;
  8.     private final String part3;
  9.     private final String part4;
  12.     public Product(String productName, String companyName, String part1, String part2, String part3, String part4) {
  13.         this.productName = productName;
  14.         this.companyName = companyName;
  15.         this.part1 = part1;
  16.         this.part2 = part2;
  17.         this.part3 = part3;
  18.         this.part4 = part4;
  19.     }
  20.     // 内部类实现构造器
  21.     static class Builder {
  22.         private String productName;
  23.         private String companyName;
  24.         private String part1;
  25.         private String part2;
  26.         private String part3;
  27.         private String part4;
  29.         public Builder productName(String productName) {
  30.             this.productName = productName;
  31.             return this;//返回自己使用时可以用链式
  32.         }
  34.         public Builder companyName(String companyName) {
  35.             this.companyName = companyName;
  36.             return this;
  37.         }
  39.         public Builder part1(String part1) {
  40.             this.part1 = part1;
  41.             return this;
  42.         }
  44.         public Builder part2(String part2) {
  45.             this.part2 = part2;
  46.             return this;
  47.         }
  49.         public Builder part3(String part3) {
  50.             this.part3 = part3;
  51.             return this;
  52.         }
  54.         public Builder part4(String part4) {
  55.             this.part4 = part4;
  56.             return this;
  57.         }
  59.         public Product build() {
  60.             return new Product(this.productName, this.companyName, this.part1, this.part2, this.part3, this.part4);
  61.         }
  62.     }
  63. }

3.2 使用

  1.  public static void main(String[] args) {
  2.         Product.Builder builder = new Product.Builder().productName("productName1").companyName("com.").part1("part1").part2("part2");
  3.         builder.part3("part3").part4("part4");
  5.         Product product = builder.build();
  6.         System.out.println(product);
  7.     }

4. 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

    5. 优点

  4. 建造者独立，易扩展。

  5. 便于控制细节风险。

    6. Spring源码中应用

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