设计模式之构造者模式

原创

罗罗的1024 2021-10-18 10:00:07 ©著作权

文章标签 java spring ide jar apache 文章分类 Java 后端开发

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定义

建造者模式（Builder Pattern）也叫做生成器模式，其定义如下：

Separate the construction of a complex object from its representation so that the same construction process can create different representations.（将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。）

示例

以构建一个人示例，灵魂是必须有的，肢体可有可无，哈哈

复用构造器

public class Person {
private String foot;
private String head;
private String face;
private String hand;
private String soul;

public Person(String soul) {
this(null,null,null,null,soul);
    }

public Person(String hand, String soul) {
this(null,null,null,hand,soul);
    }

public Person(String foot, String face, String soul) {
this(foot,null,face,null,soul);
    }

public Person(String foot, String head, String face, String hand, String soul) {
this.foot = foot;
this.head = head;
this.face = face;
this.hand = hand;
this.soul = soul;
    }
}

参数一旦多了，阅读起来就很麻烦，要理解每个参数的意思，而且一不小心还会传错

使用构造者模式

public class Person {
private String foot;
private String head;
private String face;
private String hand;
private String soul;

private Person(Builder builder) {
this.foot = builder.foot;
this.head = builder.head;
this.face = builder.face;
this.hand = builder.hand;
this.soul = builder.soul;
    }
@Override
public String toString() {
return "Builder{" +
"foot='" + foot + '\'' +
", face='" + face + '\'' +
", head='" + head + '\'' +
", hand='" + hand + '\'' +
", soul='" + soul + '\'' +
'}';
    }


public static final class Builder{
private String foot;
private String face;
private String head;
private String hand;
private String soul;

public Builder(String soul) {
this.soul = soul;
        }

public Person build(){
return new Person(this);
        }

public Builder foot(String foot) {
this.foot = foot;
return this;
        }

public Builder head(String head) {
this.head = head;
return this;
        }

public Builder face(String face) {
this.face = face;
return this;
        }

public Builder hand(String hand) {
this.hand = hand;
return this;
        }
    }
}

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

Person person = new Person.Builder("我的灵魂").face("脸庞").foot("大脚").build();
System.out.println(person);
    }
}

"C:\Program Files\Java\jdk1.8.0_144\bin\java.exe" "-javaagent:D:\IntelliJ IDEA\IntelliJ IDEA 2018.2.4\lib\idea_rt.jar=61032:D:\IntelliJ IDEA\IntelliJ IDEA 2018.2.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_144\jre\lib\charsets.jar;C:\Program bin\rep\org\springframework\spring-beans\5.2.12.RELEASE\spring-beans-5.2.12.RELEASE.jar;D:\apache-maven-3.5.4-bin\rep\org\springframework\spring-core\5.2.12.RELEASE\spring-core-5.2.12.RELEASE.jar;D:\apache-maven-3.5.4-bin\rep\org\springframework\spring-jcl\5.2.12.RELEASE\spring-jcl-5.2.12.RELEASE.jar;D:\apache-maven-3.5.4-bin\rep\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar" 
Builder{foot='大脚', face='脸庞', head='null', hand='null', soul='我的灵魂'}

Process finished with exit code 0

结合链式调用，使用起来特别直观，不易出错