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java 反射框架_Java 反射，开发框架必备技能

發(fā)布時(shí)間：2023/12/10 java 30 豆豆

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通過反射技術(shù)我們將上面的統(tǒng)一資源定位付(URL) 映射到Class 相當(dāng)于

class: news

method: list

parameter: 2

差不多就是下面樣子

class News{

public String list(String catagory_id){

...

}

我們只需要在框架核心中分析 url 然后調(diào)用對(duì)應(yīng)的方法，于此同時(shí)將參數(shù)傳遞過去。

Class>?cls?=?Class.forName("cn.netkiller.reflect.News");

Object?obj=?cls.newInstance();

Method?method?=?cls.getDeclaredMethod("list",?int.class);

return?method.invoke(obj,?2);

1.9.?Reflection 反射this.getClass().getName()?//當(dāng)前Class名字

Thread.currentThread().getStackTrace()[1].getMethodName());?//當(dāng)前方法名

1.9.1.?獲得所有變量Field[]?fields?=?objClass.getFields();

for?(Field?field?:?fields)?{

System.out.println(field.getName());

}

注意：只能去除 public變量

1.9.2.?批量賦值

1.9.3.?方法操作下載

JAVA反射調(diào)用方法的步驟有三步得到要調(diào)用類的class

得到要調(diào)用的類中的方法(Method)

方法調(diào)用(invoke)

1.9.3.1.?獲得所有方法Class>?objClass?=?a.getClass();

Method[]?methods?=??objClass.getDeclaredMethods();

for?(Method?method?:?methods)?{

System.out.println(method);

}

1.9.3.2.?set/get 方法下載package?cn.netkiller.reflect;

import?java.lang.reflect.InvocationTargetException;

import?java.lang.reflect.Method;

public?class?Member?{

public?String?name;

private?int?age;

public?String?getName()?{

return?name;

}

public?void?setName(String?name)?{

this.name?=?name;

}

public?int?getAge()?{

return?age;

}

public?void?setAge(int?age)?{

this.age?=?age;

}

@Override

public?String?toString()?{

return?"ClassA?[name="?+?name?+?",?age="?+?age?+?"]";

}

public?Member()?{

//?TODO?Auto-generated?constructor?stub

}

public?static?void?main(String[]?args)?throws?ClassNotFoundException,?InstantiationException,?IllegalAccessException,?NoSuchMethodException,?SecurityException,?IllegalArgumentException,?InvocationTargetException?{

Class>?cls?=?Class.forName("cn.netkiller.reflect.Member");

Object?member?=?cls.newInstance();

Method?setMethod?=?cls.getDeclaredMethod("setAge",?int.class);

setMethod.invoke(member,?15);

Method?getMethod?=?cls.getDeclaredMethod("getAge");

System.out.println(getMethod.invoke(member));

}

下面做一個(gè)稍微復(fù)雜點(diǎn)的例子，ClassB繼承ClassA，取出ClassA的成員變量賦值到ClassA。下載package?cn.netkiller.reflect;

public?class?ClassA?{

public?String?name;

private?int?age;

public?String?getName()?{

return?name;

}

public?void?setName(String?name)?{

this.name?=?name;

}

public?int?getAge()?{

return?age;

}

public?void?setAge(int?age)?{

this.age?=?age;

}

public?ClassA()?{

//?TODO?Auto-generated?constructor?stub

}

@Override

public?String?toString()?{

return?"ClassA?[name="?+?name?+?",?age="?+?age?+?"]";

}

package?cn.netkiller.reflect;

public?class?ClassB?extends?ClassA{

public?ClassB()?{

//?TODO?Auto-generated?constructor?stub

}

private?String?address;

public?String?getAddress()?{

return?address;

}

public?void?setAddress(String?address)?{

this.address?=?address;

}

@Override

public?String?toString()?{

return?"ClassB?[address="?+?address?+?"]";

}

package?cn.netkiller.reflect;

import?java.lang.reflect.Field;

import?java.lang.reflect.InvocationTargetException;

import?java.lang.reflect.Method;

public?class?ReflectionTest?{

public?ReflectionTest()?{

//?TODO?Auto-generated?constructor?stub

}

下載

public?void?testSetMethod()?throws?NoSuchMethodException,?SecurityException,?IllegalAccessException,?IllegalArgumentException,?InvocationTargetException,?InstantiationException?{

//?ClassA?a?=?new?ClassA();

ClassB?b?=?new?ClassB();

b.setAddress("Shenzhen");

Class?classA?=?ClassA.class;

ClassA?a?=?classA.newInstance();

a.setName("Neo");

a.setAge(30);

System.out.println(classA.getDeclaredMethod("getAge").invoke(a));

Method?m?=?classA.getDeclaredMethod("setAge",?int.class);

m.setAccessible(true);?//?因?yàn)閷懗蓀rivate?所以這里必須設(shè)置

m.invoke(b,?26);

System.out.println(a.toString());

System.out.println(b.toString());

System.out.println(b.getName());

System.out.println(b.getAge());

}

public?static?void?main(String[]?args)?throws?InvocationTargetException?{

ReflectionTest?rt?=?new?ReflectionTest();

try?{

rt.testSetMethod();

}?catch?(NoSuchMethodException?e)?{