lombok构造模式

深碍√TFBOYSˉ_ 2022-02-02 00:11 255阅读 0赞

# lombok构造模式 #

这种方法比自己写Builder类方便多了

@Data
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class DemoModel {
        private String name;
        private int age;
        private int start;
        private int end;
    }

Data注解的解释

/**
     * Generates getters for all fields, a useful toString method, and hashCode and equals implementations that check
     * all non-transient fields. Will also generate setters for all non-final fields, as well as a constructor.
     * <p>
     * Equivalent to {@code @Getter @Setter @RequiredArgsConstructor @ToString @EqualsAndHashCode}.
     * <p>
     * Complete documentation is found at <a href="https://projectlombok.org/features/Data">the project lombok features page for @Data</a>.
     * 
     * @see Getter
     * @see Setter
     * @see RequiredArgsConstructor
     * @see ToString
     * @see EqualsAndHashCode
     * @see lombok.Value
     */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.SOURCE)
    public @interface Data {
    	/**
    	 * If you specify a static constructor name, then the generated constructor will be private, and
    	 * instead a static factory method is created that other classes can use to create instances.
    	 * We suggest the name: "of", like so:
    	 * 
    	 * <pre>
    	 *     public @Data(staticConstructor = "of") class Point { final int x, y; }
    	 * </pre>
    	 * 
    	 * Default: No static constructor, instead the normal constructor is public.
    	 * 
    	 * @return Name of static 'constructor' method to generate (blank = generate a normal constructor).
    	 */
    	String staticConstructor() default "";
    }

@Builder会按builder模式生成一个内部类，具体使用如下

DemoModel model = DemoModel.builder()
                    .name("builder")
                    .age(-1)
                    .build();

注意需要写@NoArgsConstructor

这时候我们就需要添加无参构造方法，因为java序列化默认是需要一个无参构造方法。  
**这个情况是因为我们原来的IOC容器都是通过反射来获取对象实例，而对象实例一般都是单例的形式出现，这时候就需要通过无参构造方法来提供支持。**