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Java反射的基本应用
反射机制,程序在运行时加载新的类,使程序更加灵活
public class HelooReflect { public static void main(String[] args) { // 获取类 testClass(); } private static void testClass() { // 创建一个学生类的对象 Student student = new Student(); try { // 开始获取类 Class clazz1 = Student.class; Class clazz2 = student.getClass(); Class clazz3 = Class.forName("com.bjsxt.java.clc.fanshe.Student"); //判断类对象是否相等 System.out.println(clazz1 == clazz2); System.out.println(clazz1 == clazz3); //常见 方法 System.out.println("类的名字" + clazz1.getName()); System.out.println("类的简称" + clazz1.getSimpleName()); System.out.println("包的信息" + clazz1.getPackage().getName()); System.out.println("获取包名" + clazz1.getPackage()); System.out.println("获取修饰符" + clazz1.getModifiers()); System.out.println("获取父类" + clazz1.getSuperclass()); System.out.println("获取父类的超类" + clazz1.getGenericSuperclass()); System.out.println("判断是否为接口" + clazz1.isInterface()); System.out.println("获取类加载器" + clazz1.getClassLoader()); //基本类型9=(8种基本数据类型的类+1void) System.out.println(int.class == Integer.class);//不等 //判断是否是基本类型 System.out.println(int.class.isPrimitive()); System.out.println(Integer.class.isPrimitive()); System.out.println("数组是引用类型" + int[].class.isPrimitive()); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } }}
获取类的名字,方法,属性,构造器
import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.Method;public class Test2 { public static void main(String[] args) { try { Class clazz = Class.forName("bean.User"); // 获取类的名字 clazz.getName(); /** * 获取属性信息 */ // 只能获取public的属性 Field[] fields1 = clazz.getFields(); // 可以获得所有的属性 Field[] fields2 = clazz.getDeclaredFields(); // 输出获取到的属性的个数 System.out.println(fields1.length); System.out.println(fields2.length); // 遍历获取到的属性 for (Field field : fields2) { System.out.println("属性" + field); } // 获得属性的权限 Field f = clazz.getDeclaredField("uname"); System.out.println(f); /** * 获取方法的信息 */ Method[] methods = clazz.getDeclaredMethods(); Method m01 = clazz.getDeclaredMethod("getUname", null); // 如果方法有参,则必须传递参数类型对应的class对象 Method m02 = clazz.getDeclaredMethod("setUname", String.class); for (Method method : methods) { System.out.println("方法" + method); } /** *获取构造器信息 */ Constructor[] constructors = clazz.getDeclaredConstructors(); Constructor c = clazz.getDeclaredConstructor(int.class,int.class,String.class); System.out.println("获得构造器"+c); for (Constructor constructor : constructors) { System.out.println("构造器"+constructor); } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchFieldException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SecurityException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchMethodException e) { // TODO Auto-generated catch block e.printStackTrace(); } }}
通过反射操作类的属性,方法构造器
import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import bean.User;/** * @author clc * */public class Test3 { public static void main(String[] args) { try { Class<User> clazz = (Class<User>) Class.forName("bean.User"); // 通过反射API调用构造方法,构造对象 // 其实调用了User的无参构造方法 User u1 = clazz.newInstance(); System.out.println(u1); // 有参调用构造器 Constructor<User> c = clazz.getDeclaredConstructor(int.class, int.class, String.class); User u2 = c.newInstance(1234, 22, "clc"); System.out.println(u2); // 通过反射调用普通方法 User u3 = clazz.newInstance(); Method method = clazz.getDeclaredMethod("setUname", String.class); // 相当于u3.setUname("clc3"); method.invoke(u3, "clc3"); System.out.println(u3); // 通过反射操作属性 User u4 = clazz.newInstance(); Field f = clazz.getDeclaredField("uname"); // 设置属性不需要安全检查,可以直接访问 f.setAccessible(true); // 通过反射直接设置属性 f.set(u4, "clc4"); // 通过反射直接读取属性值 System.out.println(u4.getUname()); System.out.println(f.get(u4)); } catch (ClassNotFoundException 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 (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(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchFieldException e) { // TODO Auto-generated catch block e.printStackTrace(); } }}
辅助类User
package bean;public class User { private int id; private int age; private String uname; @Override public String toString() { return "User [id=" + id + ", age=" + age + ", uname=" + uname + "]"; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + age; result = prime * result + id; result = prime * result + ((uname == null) ? 0 : uname.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; User other = (User) obj; if (age != other.age) return false; if (id != other.id) return false; if (uname == null) { if (other.uname != null) return false; } else if (!uname.equals(other.uname)) return false; return true; } public int getId() { return id; } public void setId(int id) { this.id = id; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getUname() { return uname; } public void setUname(String uname) { this.uname = uname; } public User(int id, int age, String uname) { super(); this.id = id; this.age = age; this.uname = uname; } public User() { super(); }}
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import bean.User;
/**
* @author clc
*
*/
public class Test3 {
public static void main(String[] args) {
try {
Class<User> clazz = (Class<User>) Class.forName("bean.User");
// 通过反射API调用构造方法,构造对象
// 其实调用了User的无参构造方法
User u1 = clazz.newInstance();
System.out.println(u1);
// 有参调用构造器
Constructor<User> c = clazz.getDeclaredConstructor(int.class, int.class, String.class);
User u2 = c.newInstance(1234, 22, "clc");
System.out.println(u2);
// 通过反射调用普通方法
User u3 = clazz.newInstance();
Method method = clazz.getDeclaredMethod("setUname", String.class);
// 相当于u3.setUname("clc3");
method.invoke(u3, "clc3");
System.out.println(u3);
// 通过反射操作属性
User u4 = clazz.newInstance();
Field f = clazz.getDeclaredField("uname");
// 设置属性不需要安全检查,可以直接访问
f.setAccessible(true);
// 通过反射直接设置属性
f.set(u4, "clc4");
// 通过反射直接读取属性值
System.out.println(u4.getUname());
System.out.println(f.get(u4));
} catch (ClassNotFoundException 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 (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();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Java反射的基本应用
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