@Builder注解如何在Java中使用？相信很多沒有經(jīng)驗(yàn)的人對(duì)此束手無(wú)策，為此本文總結(jié)了問題出現(xiàn)的原因和解決方法，通過這篇文章希望你能解決這個(gè)問題。
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}.
*
* 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。
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重慶分公司
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(wú)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。
看完上述內(nèi)容，你們掌握@Builder注解如何在Java中使用的方法了嗎？如果還想學(xué)到更多技能或想了解更多相關(guān)內(nèi)容，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道，感謝各位的閱讀！
