手寫註解版的SpringIoc
阿新 • • 發佈:2019-04-27
根據類上的註解來建立物件
1.@component("aa"),用getBean("aa",User.class)獲取
2.@component,將類名小寫作為物件名,用getBean(User.class)獲取
package com.tedu.annotation_spring; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import java.lang.reflect.Constructor; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; /** * 根據註解來建立物件 * @author wan_ys * */ @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) @interface Component{ String value() default ""; } @Component class User{ private String name; private Integer age; public String getName() { return name; } public User(){ } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "User [name=" + name + ", age=" + age + "]"; } } public class AnnotationBeanFactory { /* * 註解的使用和反射建立物件 */ static Map<String, Object> map=new ConcurrentHashMap<String, Object>(); public <T>T createInstance(Class<T> class1) { T object =null; try { Constructor<T> constructor = class1.getDeclaredConstructor(); object= constructor.newInstance(); }catch (Exception e) { e.printStackTrace(); } //獲取註解 Component component = class1.getDeclaredAnnotation(Component.class); if (component==null) { return null; } System.out.println(component); String value = component.value(); if (value==null||"".equals(value)) { //首字母轉小寫作為物件名 String simpleName = class1.getSimpleName(); value=simpleName.substring(0,1).toLowerCase()+simpleName.substring(1); } map.put(value, object); return object; } public <T>T getBean(String key,Class<T> class1){ Object object = map.get(key); if (object==null) { object=createInstance(class1); map.put(key, object); } return (T) object; } public <T>T getBean(Class<T> class1){ //先根據類名小寫獲取key String simpleName = class1.getSimpleName(); String key=simpleName.substring(0,1).toLowerCase()+simpleName.substring(1); return getBean(key, class1); } }
簡單的測試:
package com.tedu.annotation_spring;
public class Test1 {
public static void main(String[] args) {
AnnotationBeanFactory annotationBeanFactory=new AnnotationBeanFactory();
// User user = annotationBeanFactory.createInstance(User.class);
// user.setAge(10);
// user.setName("滴滴");
// System.out.println(user);
User bean = annotationBeanFactory.getBean(User.class);
bean.setAge(11);
bean.setName("螞蟻金服");
System.out.println(b