java lombok框架

逃离我推掉我的手 2024-03-31 10:07 36阅读 0赞

#### @Data 的作用？ ####

使用这个注解，就不用再去手写Getter,Setter,equals,canEqual,hasCode,toString等方法了，注解后在编译时会自动加进去。

#### @NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor ####

@NoArgsConstructor：生成无参构造函数  
@RequiredArgsConstructor：生成一个构造函数，并对打了@NonNull的参数进行NullPointer检查 （这里有坑？为啥？）  
例如：

// 源代码
    @RequiredArgsConstructor(staticName = "of")
    class Car{
        
        @NonNull
        private String origin;
        @NonNull
        private String model;
    }

// 编译后代码
    class Car{
        
        @NonNull
        private String origin;
        @NonNull
        private String model;
        
        // 省略get、set方法
        private Car(@NonNull String origin, @NonNull String model) {
        
            if (origin == null) {
        
                throw new NullPointerException("origin is marked @NonNull but is null");
            } else {
        
                this.origin = origin;
            }
            if (model == null) {
        
                throw new NullPointerException("model is marked @NonNull but is null");
            } else {
        
                this.model = model;
            }
        }
        public static Car of(@NonNull String origin, @NonNull String model) {
        
            return new Car(origin, model);
        }
    }

@AllArgsConstructor：生成全参构造函数

> @NoArgsConstructor will generate a constructor with no parameters. If  
> this is not possible (because of final fields), a compiler error will  
> result instead, unless @NoArgsConstructor(force = true) is used, then  
> all final fields are initialized with 0 / false / null. For fields  
> with constraints, such as @NonNull fields, no check is generated,so be  
> aware that these constraints will generally not be fulfilled until  
> those fields are properly initialized later. This annotation is useful  
> primarily in combination with either @Data or one of the other  
> constructor generating annotations.

#### lombok还有什么常见用法？ ####

上面的@Data、@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor都是lombok的注解。  
其他还有：

#### @builder有什么用？ ####

当一个类的属性很多，但构造时只需要其中几个属性时，更方便。

#### @builder的原理是什么 ####

@builder自动实现了以下原生的builder模式

class Car{
        
        private String origin;
        private String model;
    
        private Car(String model){
        
            this.model = model;
        }
    
        private Car(Builder builder){
        
            this.origin = builder.origin;
            this.model = builder.model;
        }
    
        public static Car of(String model){
        
            return new Car(model);
        }
    
        public static Builder builder(){
        
            return new Builder();
        }
    
        public static class Builder{
        
            private String origin;
            private String model;
    
            public Builder origin(String origin){
        
                this.origin = origin;
                return this;
            }
    
            public Builder model(String model){
        
                this.model = model;
                return this;
            }
    
            public Car build(){
        
                return new Car(this);
            }
        }
    }

#### @SuperBuilder用法 ####