属性较多的java对象的创建

阳光穿透心脏的1/2处 2024-02-17 15:49 37阅读 0赞

之前使用的都是javabeans方式创建，如果属性较多需要多次set，在构造过程中javabean可能处于不一致的状态，比较麻烦。这时可以使用builder方式。它是不直接产生想要的对象，而是通过静态工厂的方式创建builder对象，然后再利用这个对象来set需要的对象属性。示例如下：

public class Nutrifacts {
    	private final int servingSize;
    	private final int servings;
    	private final int calories;
    	private final int sodium;
    <span style="white-space:pre">	</span>
    	// 使用静态内部类就不用依赖外部类对象来创建内部类对象
    	public static class Builder {
    		private final int servingSize;
    		private final int servings;
    		private int calories = 0;
    		private int sodium = 0;
    
    		// 设置默认参数值
    		public Builder(int servingsize, int servings) {
    			this.servingSize = servingsize;
    			this.servings = servings;
    		}
    
    		public Builder calories(int val) {
    			this.calories = val;
    			return this;
    		}
    
    		public Builder sodium(int val) {
    			this.sodium = val;
    			return this;
    		}
    
    		// 将构造好得builder对象传给外部类的构造器
    		public Nutrifacts Builder() {
    			return new Nutrifacts(this);
    		}
    	}
    
    	public Nutrifacts(Builder builder) {
    		servingSize = builder.servingSize;
    		servings = builder.servings;
    		calories = builder.calories;
    		sodium = builder.sodium;
    	}
    
    	public static void main(String[] args) {
    		// 生成对象
    		Nutrifacts nutrifacts = new Nutrifacts.Builder(0, 0).calories(0)
    				.sodium(0).Builder();
    	}
    }