PropertySource 类详解

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PropertySource 类图

PropertySource

PropertySource 类 设计用来存放对象的抽象类。同时name,source都是final在初始化后不在变化，

protected final String name;
protected final T source;

getProperty 是个抽象方法，需要在子类来实现。

equals 方法解读，

     // 当对比对象与 当前对象恒等，或者name相等，则判断相等。
    @Override
    public boolean equals(Object obj) {
        return (this == obj || (obj instanceof PropertySource &&
                ObjectUtils.nullSafeEquals(this.name, ((PropertySource) obj).name)));
    }

named()

    //  根据name 创建一个 子类 ComparisonPropertySource 对象
    public static PropertySource named(String name) {
        return new ComparisonPropertySource(name);
    }

ComparisonPropertySource 静态内部类

     // StubPropertySource  继承自  PropertySource 实现  `getProperty` 返回null 

   // ComparisonPropertySource  继承 StubPropertySource    除构造函数为全部抛出异常，一般用来创建一个具名 PropertySource
    static class ComparisonPropertySource extends StubPropertySource {

        private static final String USAGE_ERROR =
                "ComparisonPropertySource instances are for use with collection comparison only";

        public ComparisonPropertySource(String name) {
            super(name);
        }

        @Override
        public Object getSource() {
            throw new UnsupportedOperationException(USAGE_ERROR);
        }

        @Override
        public boolean containsProperty(String name) {
            throw new UnsupportedOperationException(USAGE_ERROR);
        }

        @Override
        public String getProperty(String name) {
            throw new UnsupportedOperationException(USAGE_ERROR);
        }
    }

示例代码

List> sources = new ArrayList>();
      sources.add(new MapPropertySource("sourceA", mapA));
      sources.add(new MapPropertySource("sourceB", mapB));
       sources.contains(PropertySource.named("sourceA"));
      sources.contains(PropertySource.named("sourceB"));
     !sources.contains(PropertySource.named("sourceC"));
     }
PropertySource   类重写了equals方法，named 创建一个具名的 对象

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EnumerablePropertySource

    //  重写 containsProperty  方法
    @Override
    public boolean containsProperty(String name) {
        return ObjectUtils.containsElement(getPropertyNames(), name);
    }


//   添抽样 方法，用来返回 value的 name
public abstract String[] getPropertyNames();

MapPropertySource

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以Map的形式保存 source

public class MapPropertySource extends EnumerablePropertySource> {



    public MapPropertySource(String name, Map source) {
        super(name, source);
    }
    @Override
    public Object getProperty(String name) {
        return this.source.get(name);
    }

    @Override
    public boolean containsProperty(String name) {
        return this.source.containsKey(name);
    }

    @Override
    public String[] getPropertyNames() {
        return StringUtils.toStringArray(this.source.keySet());
    }

}