java反射（详细）

￡神魔★判官ぃ 2023-01-07 15:23 185阅读 0赞

一篇关于反射的文章：（具体在代码注释中）

package com.wisdom.mix.localhost;
    
    import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Modifier;
    
    import com.hikvision.artemis.sdk.enums.Method;
    
    public class JzpTest { 
    
    	public static void main(String[] args) { 
    		//反射的作用一获取私有类的方法或者属性
    		Test test = new Test();
    		Class cls = test.getClass();
    		Constructor[] constructors;
    		//返回类的所有构造方法
    		constructors = cls.getDeclaredConstructors();
    		for(int i = 0;i<constructors.length;i++) { 
    			//构造方法的类型getModifiers
    			System.out.println(Modifier.toString(constructors[i].getModifiers())+"参数");
    			//得到构造方法的所有参数getParameterTypes
    			Class[] parameterTypes = constructors[i].getParameterTypes();
    			for(int j = 0;j<parameterTypes.length;j++) { 
    				System.out.println(parameterTypes[j].getName()+"");
    			}
    			System.out.println("-");
    		}
    		System.out.println("-------------------一阶段 得到了类中所有构造方法和构造方法中的参数----------------------");
    		System.out.println("?????如何获取特定的构造方法呢");
    		//获取无参数的构造方法。
    		try { 
    			Constructor constructor = cls.getDeclaredConstructor();
    			System.out.println(Modifier.toString(constructor.getModifiers()));
    		} catch (NoSuchMethodException e) { 
    			//可能存在没有构造方法的参数
    			e.printStackTrace();
    		}
    		//获取有两个参数分别为int和String类型的构造方法
    		Class[] p = { int.class,String.class};
    		try { 
    			Constructor constructor = cls.getDeclaredConstructor(p);
    			System.out.println(Modifier.toString(constructor.getModifiers()));
    		} catch (Exception e) { 
    			// TODO: handle exception
    		}
    		// 调用构造方法(关键)
    		//借助于newInstance方法
    		//调用public
    		Class[] pri = { String.class};
    		Object o = null;
    		try { 
    			Constructor constructorss = cls.getDeclaredConstructor(pri);
    			//这句话告诉设置权限
    			constructorss.setAccessible(true);
    			o = constructorss.newInstance("juzhongpeng");
    		} catch (NoSuchMethodException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (SecurityException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (InstantiationException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (IllegalAccessException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (IllegalArgumentException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (InvocationTargetException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		//调用类的私有方法
    		Class[] cInstance = { String.class};
    		try { 
    			java.lang.reflect.Method method = cls.getDeclaredMethod("str", cInstance);
    			method.setAccessible(true);
    			Object arg[] = { "高手都是低调且有内涵的"};
    			try { 
    				method.invoke(test, arg);
    				Field field = cls.getDeclaredField("y");
    				field.setAccessible(true);
    				field.set(o,"地表最强码者");
    			} catch (IllegalAccessException e) { 
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			} catch (InvocationTargetException e) { 
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}catch (NoSuchFieldException e) { 
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}
    		} catch (NoSuchMethodException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (SecurityException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (IllegalArgumentException e) { 
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    }

打印结果如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MTAxODE0_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MTAxODE0_size_16_color_FFFFFF_t_70]: /images/20221119/65639498655d4d3bbf25a2fbe98b5a2c.png