Java 反射

Java 反射

操作属性（Attribute，或称“域”（Field））

getFields() 和 getDeclaredFields() 方法：前者只能得到公有的属性，后者得到类中的全部属性。

为了验证两个方法的效果，编写如下的示例代码：

先创建两个类：

class Base {
    private static String basePrivateStaticField;
    protected static String baseProtectedStaticField;
    public static String basePublicStaticField;

    private String basePrivateField;
    protected String baseProtectedField;
    public String basePublicField;
}

class Derived extends Base {
    private static String derivedPrivateStaticField;
    protected static String derivedProtectedStaticField;
    public static String derivedPublicStaticField;
    
    private String derivedPrivateField;
    protected String derivedProtectedField;
    public String derivedPublicField;
}

main 函数：

public static void main(String[] args) {
    Class<Derived> derivedClass = Derived.class;

    Field[] fields = derivedClass.getFields();
    System.out.println("fields: ");
    for (Field f : fields) {
        System.out.println("  accessible: " + Modifier.toString(f.getModifiers()) + ", name: " + f.getName());
    }
    System.out.println();
    Field[] declaredFields = derivedClass.getDeclaredFields();
    System.out.println("declared fields: ");
    for (Field f : declaredFields) {
        System.out.println("  accessible: " + Modifier.toString(f.getModifiers()) + ", name: " + f.getName());
    }
}

输出如下：

fields: 
  accessible: public static, name: derivedPublicStaticField
  accessible: public, name: derivedPublicField
  accessible: public static, name: basePublicStaticField
  accessible: public, name: basePublicField

declared fields: 
  accessible: private static, name: derivedPrivateStaticField
  accessible: protected static, name: derivedProtectedStaticField
  accessible: public static, name: derivedPublicStaticField
  accessible: private, name: derivedPrivateField
  accessible: protected, name: derivedProtectedField
  accessible: public, name: derivedPublicField

可以看到，getFields() 方法获取所有的 public 属性，包括继承来的；而 getDeclaredFields() 方法获取本类的所有属性，包括 public 属性、protected 属性和 private 属性。

操作方法（Method）

参考

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