1_注解_概念
AnnoDemo1.java
package cn.itcast.annotation;
/**
* 注解javadoc演示
*
* @author itcat
* @version 1.0
* @since 1.5
*/
public class AnnoDemo1 {
/**
* 计算两数的和
* @param a 整数
* @param b 整数
* @return 两数的和
*/
public int add(int a, int b ){
return a + b;
}
}
(0)
(1)
(2)
(3)
(4)
(5)
若编码乱码,则选择ANSI编码(本地默认编码),重新生成
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2_注解_JDK内置注解
AnnoDemo2.java
package cn.itcast.annotation;
import java.util.Date;
/**
* JDK中预定义的一些注解
* * @Override ：检测被该注解标注的方法是否是继承自父类(接口)的
* * @Deprecated：该注解标注的内容，表示已过时
* * @SuppressWarnings：压制警告
*
*
*/
@SuppressWarnings("all")
public class AnnoDemo2 {
@Override
public String toString() {
return super.toString();
}
@Deprecated
public void show1(){
//有缺陷
}
public void show2(){
//替代show1方法
}
public void demo(){
show1();
Date date = new Date();
}
}
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3_注解_自定义注解_格式&本质 (1)
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4_注解_自定义注解_属性定义
Person.java
package cn.itcast.annotation;
public enum Person {
P1,P2;//枚举
}
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MyAnno2.java
package cn.itcast.annotation;
public @interface MyAnno2 {
}
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MyAnno.java
package cn.itcast.annotation;
import com.sun.corba.se.spi.orbutil.threadpool.Work;
public @interface MyAnno {
int value();
Person per();
MyAnno2 anno2();
String[] strs();
/*String name() default "张三";*/
/*String show2();
Person per();
MyAnno2 anno2();
String[] strs();*/
}
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Worker.java
package cn.itcast.annotation;
@MyAnno(value=12,per = Person.P1,anno2 = @MyAnno2,strs="bbb")
@MyAnno3
public class Worker {
@MyAnno3
public String name = "aaa";
@MyAnno3
public void show(){
}
}
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5_注解_自定义注解_元注解
(1)@Target
使用:
(2)@Retention
(3)@Documented:加了注解之后,会在javaAPI文档中体现
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6_注解_解析注解
注解是用来替换配置文件的
ReflectTest.java
package cn.itcast.annotation;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.Properties;
/**
* 框架类
*/
@Pro(className = "cn.itcast.annotation.Demo1",methodName = "show")
public class ReflectTest {
public static void main(String[] args) throws Exception {
/*
前提：不能改变该类的任何代码。可以创建任意类的对象，可以执行任意方法
*/
//1.解析注解
//1.1获取该类的字节码文件对象
Class<ReflectTest> reflectTestClass = ReflectTest.class;
//2.获取上边的注解对象
//其实就是在内存中生成了一个该注解接口的子类实现对象
/*
public class ProImpl implements Pro{
public String className(){
return "cn.itcast.annotation.Demo1";
}
public String methodName(){
return "show";
}
}
*/
Pro an = reflectTestClass.getAnnotation(Pro.class);
//3.调用注解对象中定义的抽象方法，获取返回值
String className = an.className();
String methodName = an.methodName();
System.out.println(className);
System.out.println(methodName);
//3.加载该类进内存
Class cls = Class.forName(className);
//4.创建对象
Object obj = cls.newInstance();
//5.获取方法对象
Method method = cls.getMethod(methodName);
//6.执行方法
method.invoke(obj);
}
}
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7_注解_案例_简单的测试框架
Calculator.java
package cn.itcast.annotation.demo;
/**
* 小明定义的计算器类
*/
public class Calculator {
//加法
@Check
public void add(){
String str = null;
str.toString();
System.out.println("1 + 0 =" + (1 + 0));
}
//减法
@Check
public void sub(){
System.out.println("1 - 0 =" + (1 - 0));
}
//乘法
@Check
public void mul(){
System.out.println("1 * 0 =" + (1 * 0));
}
//除法
@Check
public void div(){
System.out.println("1 / 0 =" + (1 / 0));
}
public void show(){
System.out.println("永无bug...");
}
}
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Check.java
package cn.itcast.annotation.demo;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Check {
}
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TestCheck.java
package cn.itcast.annotation.demo;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* 简单的测试框架
*
* 当主方法执行后，会自动自行被检测的所有方法(加了Check注解的方法)，判断方法是否有异常，记录到文件中
*/
public class TestCheck {
public static void main(String[] args) throws IOException {
//1.创建计算器对象
Calculator c = new Calculator();
//2.获取字节码文件对象
Class cls = c.getClass();
//3.获取所有方法
Method[] methods = cls.getMethods();
int number = 0;//出现异常的次数
BufferedWriter bw = new BufferedWriter(new FileWriter("bug.txt"));
for (Method method : methods) {
//4.判断方法上是否有Check注解
if(method.isAnnotationPresent(Check.class)){
//5.有，执行
try {
method.invoke(c);
} catch (Exception e) {
//6.捕获异常
//记录到文件中
number ++;
bw.write(method.getName()+ " 方法出异常了");
bw.newLine();
bw.write("异常的名称:" + e.getCause().getClass().getSimpleName());
bw.newLine();
bw.write("异常的原因:"+e.getCause().getMessage());
bw.newLine();
bw.write("--------------------------");
bw.newLine();
}
}
}
bw.write("本次测试一共出现 "+number+" 次异常");
bw.flush();
bw.close();
}
}
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