?Java Builder模式：是Java設(shè)計(jì)模式之一，它屬于對(duì)象創(chuàng)建型模式，是將一個(gè)復(fù)雜對(duì)象的構(gòu)建與它的表示分離，使得同樣的構(gòu)建過程可以創(chuàng)建不同的表示。

結(jié)論一：使用lombok的@Data和@Builder注解構(gòu)建Java類的Builder簡(jiǎn)潔高效，推薦實(shí)際應(yīng)用。
結(jié)論二：手動(dòng)編寫Java類的Builder，能夠全貌理解Builder模式，推薦試試。
結(jié)論三：Java類的Builder模式，最大好處就是構(gòu)建對(duì)象時(shí)，可以靈活構(gòu)建需要的屬性。

1.1普通Java類.

1.1.1普通Java對(duì)象

普通Java類，一般有屬性、set、get、toString方法。

public class City01Response implements Serializable {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;public City01Response() {}public boolean isSuccess() {return success;}public void setSuccess(boolean success) {this.success = success;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public Long getCityId() {return cityId;}public void setCityId(Long cityId) {this.cityId = cityId;}public String getCityName() {return cityName;}public void setCityName(String cityName) {this.cityName = cityName;}public String getCityDescribe() {return cityDescribe;}public void setCityDescribe(String cityDescribe) {this.cityDescribe = cityDescribe;}@Overridepublic String toString() {return "City01Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";}
}

1.2普通Java類使用@Data注解

1.2.1普通Java類

使用@Data注解后，普通Java類，只有屬性。set、get、toString方法由@Data注解接管。使用方式等價(jià)。

@Data
public class City01Response implements Serializable {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;
}

1.3手動(dòng)編寫Java類的Builder(靜態(tài)內(nèi)部類)

1.3.1手動(dòng)編寫Java類的Builder

本例內(nèi)部類使用靜態(tài)類實(shí)現(xiàn)，build使用靜態(tài)方法。
普通Java類：City02Response
(1)編寫普通Java類：City02Response，一般有屬性、set、get、toString方法。
(2)在普通Java類：City02Response中，編寫一個(gè)內(nèi)部類：City02ResponseBuilder。
(3)在普通Java類：City02Response中，實(shí)現(xiàn)一個(gè)builder方法，創(chuàng)建一個(gè)內(nèi)部類City02ResponseBuilder的對(duì)象。
(4)在內(nèi)部類：City02ResponseBuilder中，實(shí)現(xiàn)一個(gè)build方法，返回普通Java類：City02Response的對(duì)象。
(5)在內(nèi)部類：City02ResponseBuilder中。為每個(gè)屬性實(shí)現(xiàn)一個(gè)設(shè)置方法，并且返回City02ResponseBuilder對(duì)象本身，即返回this。

public class City02Response implements Serializable {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;public static City02Response.City02ResponseBuilder builder() {return new City02Response.City02ResponseBuilder();}public static City02Response getCityInfoSuccess(Long cityID, String cityName, String cityDescribe) {return builder().success(true).msg("獲取城市信息成功").cityId(cityID).cityName(cityName).cityDescribe(cityDescribe).build();}public static City02Response getCityInfoFail(Long cityID, String failMsg) {return builder().success(false).msg(failMsg).cityId(cityID).build();}public City02Response() {}public City02Response(boolean success, String msg, Long cityId, String cityName, String cityDescribe) {this.success = success;this.msg = msg;this.cityId = cityId;this.cityName = cityName;this.cityDescribe = cityDescribe;}@Overridepublic String toString() {return "City02Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";}public boolean isSuccess() {return success;}public void setSuccess(boolean success) {this.success = success;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public Long getCityId() {return cityId;}public void setCityId(Long cityId) {this.cityId = cityId;}public String getCityName() {return cityName;}public void setCityName(String cityName) {this.cityName = cityName;}public String getCityDescribe() {return cityDescribe;}public void setCityDescribe(String cityDescribe) {this.cityDescribe = cityDescribe;}public static class City02ResponseBuilder {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;City02ResponseBuilder() {}public City02Response build() {return new City02Response(success, msg, cityId, cityName, cityDescribe);}public City02Response.City02ResponseBuilder success(final boolean success) {this.success = success;return this;}public City02Response.City02ResponseBuilder msg(final String msg) {this.msg = msg;return this;}public City02Response.City02ResponseBuilder cityId(final Long cityId) {this.cityId = cityId;return this;}public City02Response.City02ResponseBuilder cityName(final String cityName) {this.cityName = cityName;return this;}public City02Response.City02ResponseBuilder cityDescribe(final String cityDescribe) {this.cityDescribe = cityDescribe;return this;}@Overridepublic String toString() {return "City02ResponseBuilder.City02Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";}}
}

1.3.2代碼中的getCityInfoSuccess和getCityInfoFail是對(duì)builder封裝使用

代碼中的getCityInfoSuccess和getCityInfoFail是對(duì)builder封裝應(yīng)用。不是必須部分。

1.4使用lombok的@Data和@Builder注解構(gòu)建Java對(duì)象的Builder

1.4.1使用@Data和@Builder注解

使用@Data和@Builder注解，簡(jiǎn)化代碼，效果等價(jià)。需引入jar包。

<dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.24</version>
</dependency>

@Data
@Builder
public class City03Response implements Serializable {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;public static City03Response getCityInfoSuccess(Long cityID, String cityName, String cityDescribe) {return builder().success(true).msg("獲取城市信息成功").cityId(cityID).cityName(cityName).cityDescribe(cityDescribe).build();}public static City03Response getCityInfoFail(Long cityID, String failMsg) {return builder().success(false).msg(failMsg).cityId(cityID).build();}
}

1.4.2代碼中的getCityInfoSuccess和getCityInfoFail是對(duì)builder封裝使用

代碼中的getCityInfoSuccess和getCityInfoFail是對(duì)builder封裝應(yīng)用。不是必須部分。

1.5普通Jave類和Builder類分開

1.5.1普通Java類

public class City04Response {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;public City04Response(boolean success, String msg, Long cityId, String cityName, String cityDescribe) {this.success = success;this.msg = msg;this.cityId = cityId;this.cityName = cityName;this.cityDescribe = cityDescribe;}public boolean isSuccess() {return success;}public void setSuccess(boolean success) {this.success = success;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public Long getCityId() {return cityId;}public void setCityId(Long cityId) {this.cityId = cityId;}public String getCityName() {return cityName;}public void setCityName(String cityName) {this.cityName = cityName;}public String getCityDescribe() {return cityDescribe;}public void setCityDescribe(String cityDescribe) {this.cityDescribe = cityDescribe;}@Overridepublic String toString() {return "City04Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";}
}

1.5.2普通Java類的Builder類

public class City04ResponseBuilder implements Serializable {private boolean success;private String msg;private Long cityId;private String cityName;private String cityDescribe;public City04ResponseBuilder setSuccess(boolean success) {this.success = success;return this;}public City04ResponseBuilder setMsg(String msg) {this.msg = msg;return this;}public City04ResponseBuilder setCityId(Long cityId) {this.cityId = cityId;return this;}public City04ResponseBuilder setCityName(String cityName) {this.cityName = cityName;return this;}public City04ResponseBuilder setCityDescribe(String cityDescribe) {this.cityDescribe = cityDescribe;return this;}public City04Response build() {return new City04Response(success, msg, cityId, cityName, cityDescribe);}
}

1.6測(cè)試

public class UseBuildUtils {public static void main(String[] args) {City02Response city02Response;System.out.println("原生的Builder的Java對(duì)象,City02Response的Builder使用:");city02Response = City02Response.builder().success(true).msg("獲取城市信息成功").cityId(20230328L).cityName("杭州").cityDescribe("杭州是一個(gè)互聯(lián)網(wǎng)城市").build();System.out.println("City02Response直接使用builder: " +city02Response.toString());city02Response = City02Response.getCityInfoSuccess(20230328L, "杭州", "杭州是一個(gè)互聯(lián)網(wǎng)城市");System.out.println("City02Response獲取成功: " +city02Response.toString());city02Response = City02Response.getCityInfoFail(20230328L, "網(wǎng)絡(luò)異常,無法獲取信息");System.out.println("City02Response獲取失敗: " +city02Response.toString());City03Response city03Response;System.out.println("基于注解@Data和@Builder的Java對(duì)象,city03Response的Builder使用:");city03Response = City03Response.builder().success(true).msg("獲取城市信息成功").cityId(20230328L).cityName("蘇州").cityDescribe("工業(yè)城市").build();System.out.println("city03Response直接使用builder: " +city03Response.toString());city03Response = City03Response.getCityInfoSuccess(20230328L, "蘇州", "工業(yè)城市");System.out.println("city03Response獲取成功: " +city03Response.toString());city03Response = City03Response.getCityInfoFail(20230328L, "網(wǎng)絡(luò)異常,無法獲取信息");System.out.println("city03Response獲取失敗: " +city03Response.toString());System.out.println("普通Java類和Builder類分開場(chǎng)景的Builder使用:");City04Response city04Response = new City04ResponseBuilder().setSuccess(true).setMsg("獲取城市信息成功").setCityId(20230328L).setCityName("寧波").setCityDescribe("港口城市").build();System.out.println("city04Response獲取成功:"+city04Response.toString());}
}

原生的Builder的Java對(duì)象,City02Response的Builder使用:
City02Response直接使用builder: City02Response(success=true, msg=獲取城市信息成功, cityId=20230328, cityName=杭州, cityDescribe=杭州是一個(gè)互聯(lián)網(wǎng)城市)
City02Response獲取成功: City02Response(success=true, msg=獲取城市信息成功, cityId=20230328, cityName=杭州, cityDescribe=杭州是一個(gè)互聯(lián)網(wǎng)城市)
City02Response獲取失敗: City02Response(success=false, msg=網(wǎng)絡(luò)異常,無法獲取信息, cityId=20230328, cityName=null, cityDescribe=null)

基于注解@Data和@Builder的Java對(duì)象,city03Response的Builder使用:
city03Response直接使用builder: City03Response(success=true, msg=獲取城市信息成功, cityId=20230328, cityName=蘇州, cityDescribe=工業(yè)城市)
city03Response獲取成功: City03Response(success=true, msg=獲取城市信息成功, cityId=20230328, cityName=蘇州, cityDescribe=工業(yè)城市)
city03Response獲取失敗: City03Response(success=false, msg=網(wǎng)絡(luò)異常,無法獲取信息, cityId=20230328, cityName=null, cityDescribe=null)

普通Java類和Builder類分開場(chǎng)景的Builder使用:
city04Response獲取成功:City04Response(success=true, msg=獲取城市信息成功, cityId=20230328, cityName=寧波, cityDescribe=港口城市)