Lombok中@Builder用法

1、建造者模式簡(jiǎn)介：Builder 使用創(chuàng)建者模式又叫建造者模式。簡(jiǎn)單來說，就是一步步創(chuàng)建一個(gè)對(duì)象，它對(duì)用戶屏蔽了里面構(gòu)建的細(xì)節(jié)，但卻可以精細(xì)地控制對(duì)象的構(gòu)造過程。

2、注解類Builder.java注釋：

* The builder annotation creates a so-called 'builder' aspect to the class that is annotated or the class
 * that contains a member which is annotated with {@code @Builder}.
 * <p>
 * If a member is annotated, it must be either a constructor or a method. If a class is annotated,
 * then a private constructor is generated with all fields as arguments
 * (as if {@code @AllArgsConstructor(access = AccessLevel.PRIVATE)} is present
 * on the class), and it is as if this constructor has been annotated with {@code @Builder} instead.
 * Note that this constructor is only generated if you haven't written any constructors and also haven't
 * added any explicit {@code @XArgsConstructor} annotations. In those cases, lombok will assume an all-args
 * constructor is present and generate code that uses it; this means you'd get a compiler error if this
 * constructor is not present.

在企業(yè)開發(fā)中，一般在領(lǐng)域?qū)ο髮?shí)體上標(biāo)注@Builder，其作用就相當(dāng)于@AllArgsConstructor(access = AccessLevel.PRIVATE),@Builder一般與@Getter結(jié)合使用。

3、實(shí)戰(zhàn)
① 編寫測(cè)試實(shí)體類。

import lombok.Builder;
import lombok.Getter;

@Builder
//@Getter
public class Person {
  private String name;

  private String id;

  private String phoneNumeber;
}

② 編寫測(cè)試類。

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


    Person.PersonBuilder builder = Person.builder();
    builder.phoneNumeber("11111")
        .id("1123")
        .name("asdd").build();
    System.out.println(builder);


  }
}

③編譯并執(zhí)行的結(jié)果為：
Person.PersonBuilder(name=asdd, id=1123, phoneNumeber=11111)

④ 編譯后的字節(jié)碼分析：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.atyunniao;

public class Person {
  private String name;
  private String id;
  private String phoneNumeber;

  Person(String name, String id, String phoneNumeber) {
    this.name = name;
    this.id = id;
    this.phoneNumeber = phoneNumeber;
  }

  public static Person.PersonBuilder builder() {
    return new Person.PersonBuilder();
  }

  public String getName() {
    return this.name;
  }

  public String getId() {
    return this.id;
  }

  public String getPhoneNumeber() {
    return this.phoneNumeber;
  }

  public static class PersonBuilder {
    private String name;
    private String id;
    private String phoneNumeber;

    PersonBuilder() {
    }

    public Person.PersonBuilder name(String name) {
      this.name = name;
      return this;
    }

    public Person.PersonBuilder id(String id) {
      this.id = id;
      return this;
    }

    public Person.PersonBuilder phoneNumeber(String phoneNumeber) {
      this.phoneNumeber = phoneNumeber;
      return this;
    }

    public Person build() {
      return new Person(this.name, this.id, this.phoneNumeber);
    }

    public String toString() {
      return "Person.PersonBuilder(name=" + this.name + ", id=" + this.id + ", phoneNumeber=" + this.phoneNumeber + ")";
    }
  }
}

@Builder的作用：
生成一個(gè)全屬性的構(gòu)造器
生成了一個(gè)返回靜態(tài)內(nèi)部類PersonBuilder對(duì)象的方法
生成了一個(gè)靜態(tài)內(nèi)部類PersonBuilder，這個(gè)靜態(tài)內(nèi)部類包含Person類的三個(gè)屬性，無參構(gòu)造器，三個(gè)方法名為屬性名的方法，返回Person對(duì)象的build方法，輸出靜態(tài)內(nèi)部類三個(gè)屬性的toString()方法。

⑤ 建造者使用過程：

 Person.PersonBuilder builder = Person.builder();
    builder.phoneNumeber("11111")
        .id("1123")
        .name("asdd").build();
    System.out.println(builder);

先實(shí)例化內(nèi)部類對(duì)象并返回，然后為調(diào)用內(nèi)部類的方法為內(nèi)部類的屬性賦值，build()方法就是將內(nèi)部類PersonBuilder的屬性值傳入Person構(gòu)造器中，實(shí)例化Person對(duì)象。

以上即為對(duì)于@Builder的簡(jiǎn)單使用。

到此這篇關(guān)于Java中l(wèi)ombok的@Builder注解的解析與簡(jiǎn)單使用詳解的文章就介紹到這了,更多相關(guān)java lombok的@Builder注解內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

最新評(píng)論