1 package com.yubaby.reflect;
2
3 import com.yubaby.domain.Person;
4
5 import java.lang.reflect.Constructor;
6 import java.lang.reflect.Field;
7 import java.lang.reflect.Method;
8
9 /*
10 Class对象功能：
11 * getXxx()只能获取到public权限修饰的
12 * getDeclaredXxx()各种访问权限修饰的都能获取到
13
14 * 获取功能：
15 1. 获取成员变量
16 * Field[] getFields() 获取所有public修饰的成员变量
17 * Field getField(String name) 获取指定名称的 public修饰的成员变量
18 * Field[] getDeclaredFields() 获取所有的成员变量，不考虑修饰符
19 * Field getDeclaredField(String name) 获取指定名称的成员变量，不考虑修饰符
20
21 * Field：成员变量
22 * 操作：
23 1. 设置值
24 * void set(Object obj, Object value)
25 2. 获取值
26 * get(Object obj)
27 3. 忽略访问权限修饰符的安全检查
28 * setAccessible(true):暴力反射
29 * 构造方法、成员方法也都支持暴力反射
30
31 2. 获取构造方法
32 * Constructor<?>[] getConstructors()
33 * Constructor<T> getConstructor(类<?>... parameterTypes)
34 * Constructor<T> getDeclaredConstructor(类<?>... parameterTypes)
35 * Constructor<?>[] getDeclaredConstructors()
36
37 * Constructor:构造方法
38 * 创建对象：
39 * T newInstance(Object... initargs)
40 * 如果使用空参数构造方法创建对象，操作可以简化：Class对象的newInstance方法
41
42 3. 获取成员方法
43 * Method[] getMethods()
44 * Method getMethod(String name, 类<?>... parameterTypes)
45 * Method[] getDeclaredMethods()
46 * Method getDeclaredMethod(String name, 类<?>... parameterTypes)
47
48 * Method：方法对象
49 * 执行方法：
50 * Object invoke(Object obj, Object... args)
51 * 获取方法名称：
52 * String getName:获取方法名
53
54 4. 获取全类名
55 * String getName()
56 */
57 public class ReflectDemo2 {
58 public static void main(String[] args) throws Exception {
59 // learnField();
60 // learnConstructor();
61 learnMethod();
62 }
63
64 private static void learnField() throws Exception{
65 Class<Person> personClass = Person.class; //获取Person类的Class对象
66
67 // 1.1 Field[] getFields()
68 Field[] fields = personClass.getFields();
69 for (Field field: fields){
70 System.out.println(field);
71 }
72 //public int com.yubaby.domain.Person.a
73
74 System.out.println("--------------------");
75
76 //1.2 Field getField(String name)
77 Field a = personClass.getField("a");
78 //获取成员变量a的值
79 Person person = new Person();
80 Object value = a.get(person);
81 System.out.println(value); //int变量未赋值时，默认值为0
82 //设置a的值
83 a.set(person, 100);
84 System.out.println(person); //Person{name='null', age=0, a=100, b=0, c=0, d=0}
85
86 System.out.println("--------------------");
87
88 //1.3 Field[] getDeclaredFields()
89 Field[] declaredFields = personClass.getDeclaredFields();
90 for (Field field: declaredFields){
91 System.out.println(field);
92 }
93 /*
94 private java.lang.String com.yubaby.domain.Person.name
95 private int com.yubaby.domain.Person.age
96 public int com.yubaby.domain.Person.a
97 protected int com.yubaby.domain.Person.b
98 int com.yubaby.domain.Person.c
99 private int com.yubaby.domain.Person.d
100 */
101
102 System.out.println("--------------------");
103
104 //1.4 Field getDeclaredField(String name)
105 /*Field d = personClass.getDeclaredField("d");
106 Object value2 = d.get(person); //报错，非法访问异常
107 System.out.println(value2);*/
108 Field d = personClass.getDeclaredField("d");
109 d.setAccessible(true); //暴力反射：忽略访问权限修饰符的安全检查
110 Object value2 = d.get(person); //0
111 System.out.println(value2);
112 }
113
114 private static void learnConstructor() throws Exception{
115 Class<Person> personClass = Person.class;
116
117 //2.1 Constructor<?>[] getConstructors()
118 Constructor<Person> constructor = personClass.getConstructor();
119 System.out.println(constructor); //public com.yubaby.domain.Person()
120 //创建对象
121 Person person = constructor.newInstance();
122 System.out.println(person); //Person{name='null', age=0, a=0, b=0, c=0, d=0}
123 //无参构造方法创建对象是的简化操作
124 // Person person2 = personClass.newInstance();
125 // System.out.println(person2); ////Person{name='null', age=0, a=0, b=0, c=0, d=0}
126
127 //2.2 Constructor<T> getConstructor(类<?>... parameterTypes)
128 Constructor<Person> constructor1 = personClass.getConstructor(String.class, int.class);
129 System.out.println(constructor1); //public com.yubaby.domain.Person(java.lang.String,int)
130 //创建对象
131 Person person1 = constructor1.newInstance("tom", 24);
132 System.out.println(person1); //Person{name='tom', age=24, a=0, b=0, c=0, d=0}
133
134 //2.3 Constructor<T> getDeclaredConstructor(类<?>... parameterTypes)
135 //2.4 Constructor<?>[] getDeclaredConstructors()
136 }
137
138 private static void learnMethod() throws Exception{
139 Class<Person> personClass = Person.class;
140
141 //3.1 Method[] getMethods()
142 Method eatMethod = personClass.getMethod("eat");
143 Person person = new Person();
144 person.eat(); //eat...
145 eatMethod.invoke(person); //eat...
146
147 //获取方法名
148 System.out.println(eatMethod.getName()); //eat
149 //获取类名
150 System.out.println(personClass.getName()); //com.yubaby.domain.Person <-- 全类名：含有包名
151
152 Method eatMethod2 = personClass.getMethod("eat", String.class);
153 person.eat("米饭"); //eat:米饭
154 eatMethod2.invoke(person, "面条"); //eat:面条
155 System.out.println(eatMethod.getName()); //eat
156
157 //3.2 Method getMethod(String name, 类<?>... parameterTypes)
158 Method[] methods = personClass.getMethods();
159 for (Method method: methods){
160 System.out.println(method);
161 }
162 /*
163 包含有父类Object类的方法
164 public java.lang.String com.yubaby.domain.Person.getName()
165 public java.lang.String com.yubaby.domain.Person.toString()
166 public void com.yubaby.domain.Person.setName(java.lang.String)
167 public void com.yubaby.domain.Person.setAge(int)
168 public int com.yubaby.domain.Person.getAge()
169 public void com.yubaby.domain.Person.eat()
170 public void com.yubaby.domain.Person.eat(java.lang.String)
171 public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException
172 public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException
173 public final void java.lang.Object.wait() throws java.lang.InterruptedException
174 public boolean java.lang.Object.equals(java.lang.Object)
175 public native int java.lang.Object.hashCode()
176 public final native java.lang.Class java.lang.Object.getClass()
177 public final native void java.lang.Object.notify()
178 public final native void java.lang.Object.notifyAll()
179 */
180
181 //3.3 Method[] getDeclaredMethods()
182 //3.4 Method getDeclaredMethod(String name, 类<?>... parameterTypes)
183 }
184 }
1 package com.yubaby.domain;
2
3 public class Person {
4 private String name;
5 private int age;
6
7 public int a;
8 protected int b;
9 int c;
10 private int d;
11
12 public Person() {
13 }
14
15 public Person(String name, int age) {
16 this.name = name;
17 this.age = age;
18 }
19
20 public void setName(String name) {
21 this.name = name;
22 }
23
24 public void setAge(int age) {
25 this.age = age;
26 }
27
28 public String getName() {
29 return name;
30 }
31
32 public int getAge() {
33 return age;
34 }
35
36 @Override
37 public String toString() {
38 return "Person{" +
39 "name='" + name + '\'' +
40 ", age=" + age +
41 ", a=" + a +
42 ", b=" + b +
43 ", c=" + c +
44 ", d=" + d +
45 '}';
46 }
47
48 public void eat(){
49 System.out.println("eat...");
50 }
51
52 public void eat(String food){ //函数重载
53 System.out.println("eat:" + food);
54 }
55 }
