Java类的Builder应用以及使用@Data和@Builder高效应用Builder

r囧r小猫 2024-04-23 02:57 75阅读 0赞

**记录**：395

**场景**：手动编写Java类的Builder及其应用。使用lombok的@Data和@Builder注解构建Java类的Builder及其应用。

**Java Builder模式**：是Java设计模式之一，它属于对象创建型模式，是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。

**结论一**：使用lombok的@Data和@Builder注解构建Java类的Builder简洁高效，推荐实际应用。

**结论二**：手动编写Java类的Builder，能够全貌理解Builder模式，推荐试试。

**结论三**：Java类的Builder模式，最大好处就是构建对象时，可以灵活构建需要的属性。

**7.1普通Java类**

**7.1.1普通Java对象**

普通Java类，一般有属性、set、get、toString方法。

**7.1.2代码**

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;
      }
      @Override
      public String toString() {
          return "City01Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";
      }
    }

**7.2普通Java类使用@Data注解**

**7.2.1普通Java类**

使用@Data注解后，普通Java类，只有属性。set、get、toString方法由@Data注解接管。使用方式等价。

**7.2.2代码**

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

**7.3手动编写Java类的Builder(静态内部类)**

**7.3.1手动编写Java类的Builder**

本例内部类使用静态类实现，build使用静态方法。

普通Java类：City02Response

(1)编写普通Java类：City02Response，一般有属性、set、get、toString方法。

(2)在普通Java类：City02Response中，编写一个内部类：City02ResponseBuilder。

(3)在普通Java类：City02Response中，实现一个builder方法，创建一个内部类City02ResponseBuilder的对象。

(4)在内部类：City02ResponseBuilder中，实现一个build方法，返回普通Java类：City02Response的对象。

(5)在内部类：City02ResponseBuilder中。为每个属性实现一个设置方法，并且返回City02ResponseBuilder对象本身，即返回this。

**7.3.2代码**

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("获取城市信息成功").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;
      }
      @Override
      public 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;
        }
        @Override
        public String toString() {
            return "City02ResponseBuilder.City02Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";
        }
      }
    }

**7.3.3代码中的getCityInfoSuccess和getCityInfoFail是对builder封装使用**

代码中的getCityInfoSuccess和getCityInfoFail是对builder封装应用。不是必须部分。

**7.4使用lombok的@Data和@Builder注解构建Java对象的Builder**

**7.4.1使用@Data和@Builder注解**

使用@Data和@Builder注解，简化代码，效果等价。需引入jar包。

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

**7.4.2代码**

@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("获取城市信息成功").cityId(cityID).cityName(cityName).cityDescribe(cityDescribe).build();
      }
      public static City03Response getCityInfoFail(Long cityID, String failMsg) {
        return builder().success(false).msg(failMsg).cityId(cityID).build();
      }
    }

**7.4.3代码中的getCityInfoSuccess和getCityInfoFail是对builder封装使用**

代码中的getCityInfoSuccess和getCityInfoFail是对builder封装应用。不是必须部分。

**7.5普通Jave类和Builder类分开**

**7.5.1普通Java类**

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;
      }
      @Override
      public String toString() {
        return "City04Response(" + "success=" + success + ", msg=" + msg + ", cityId=" + cityId + ", cityName=" + cityName + ", cityDescribe=" + cityDescribe + ")";
      }
    }

**7.5.2普通Java类的Builder类**

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);
      }
    }

**7.6应用**

**7.6.1测试**

public class UseBuildUtils {
      public static void main(String[] args) {
        City02Response city02Response;
        System.out.println("原生的Builder的Java对象,City02Response的Builder使用:");
        city02Response = City02Response.builder().success(true).msg("获取城市信息成功").cityId(20230328L).cityName("杭州").cityDescribe("杭州是一个互联网城市").build();
        System.out.println("City02Response直接使用builder: " +city02Response.toString());
        city02Response = City02Response.getCityInfoSuccess(20230328L, "杭州", "杭州是一个互联网城市");
        System.out.println("City02Response获取成功: " +city02Response.toString());
        city02Response = City02Response.getCityInfoFail(20230328L, "网络异常,无法获取信息");
        System.out.println("City02Response获取失败: " +city02Response.toString());
        City03Response city03Response;
        System.out.println("基于注解@Data和@Builder的Java对象,city03Response的Builder使用:");
        city03Response = City03Response.builder().success(true).msg("获取城市信息成功").cityId(20230328L).cityName("苏州").cityDescribe("工业城市").build();
        System.out.println("city03Response直接使用builder: " +city03Response.toString());
        city03Response = City03Response.getCityInfoSuccess(20230328L, "苏州", "工业城市");
        System.out.println("city03Response获取成功: " +city03Response.toString());
        city03Response = City03Response.getCityInfoFail(20230328L, "网络异常,无法获取信息");
        System.out.println("city03Response获取失败: " +city03Response.toString());
        System.out.println("普通Java类和Builder类分开场景的Builder使用:");
        City04Response city04Response = new City04ResponseBuilder().setSuccess(true).setMsg("获取城市信息成功").setCityId(20230328L).setCityName("宁波").setCityDescribe("港口城市").build();
        System.out.println("city04Response获取成功:"+city04Response.toString());
      }
    }

**7.6.2打印**

原生的Builder的Java对象,City02Response的Builder使用:
    City02Response直接使用builder: City02Response(success=true, msg=获取城市信息成功, cityId=20230328, cityName=杭州, cityDescribe=杭州是一个互联网城市)
    City02Response获取成功: City02Response(success=true, msg=获取城市信息成功, cityId=20230328, cityName=杭州, cityDescribe=杭州是一个互联网城市)
    City02Response获取失败: City02Response(success=false, msg=网络异常,无法获取信息, cityId=20230328, cityName=null, cityDescribe=null)
    基于注解@Data和@Builder的Java对象,city03Response的Builder使用:
    city03Response直接使用builder: City03Response(success=true, msg=获取城市信息成功, cityId=20230328, cityName=苏州, cityDescribe=工业城市)
    city03Response获取成功: City03Response(success=true, msg=获取城市信息成功, cityId=20230328, cityName=苏州, cityDescribe=工业城市)
    city03Response获取失败: City03Response(success=false, msg=网络异常,无法获取信息, cityId=20230328, cityName=null, cityDescribe=null)
    普通Java类和Builder类分开场景的Builder使用:
    city04Response获取成功:City04Response(success=true, msg=获取城市信息成功, cityId=20230328, cityName=宁波, cityDescribe=港口城市)

以上，感谢。

2023年3月29日