怎么查詢網(wǎng)站備案培訓(xùn)學(xué)校怎么招生
目錄
- 4、原理-手寫IoC
- 4.1、回顧Java反射
- 4.2、實(shí)現(xiàn)Spring的IoC
4、原理-手寫IoC
我們都知道，Spring框架的IOC是基于Java反射機(jī)制實(shí)現(xiàn)的，下面我們先回顧一下java反射。
4.1、回顧Java反射
Java反射機(jī)制是在運(yùn)行狀態(tài)中，對(duì)于任意一個(gè)類，都能夠知道這個(gè)類的所有屬性和方法；對(duì)于任意一個(gè)對(duì)象，都能夠調(diào)用它的任意方法和屬性；這種動(dòng)態(tài)獲取信息以及動(dòng)態(tài)調(diào)用對(duì)象方法的功能稱為Java語(yǔ)言的反射機(jī)制。簡(jiǎn)單來(lái)說(shuō)，反射機(jī)制指的是程序在運(yùn)行時(shí)能夠獲取自身的信息。
要想解剖一個(gè)類，必須先要獲取到該類的Class對(duì)象。而剖析一個(gè)類或用反射解決具體的問(wèn)題就是使用相關(guān)API**（1）java.lang.Class（2）java.lang.reflect**，所以，Class對(duì)象是反射的根源。
自定義類
package com.atguigu.reflect;public class Car {//屬性private String name;private int age;private String color;//無(wú)參數(shù)構(gòu)造public Car() {}//有參數(shù)構(gòu)造public Car(String name, int age, String color) {this.name = name;this.age = age;this.color = color;}//普通方法private void run() {System.out.println("私有方法-run.....");}//get和set方法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 String getColor() {return color;}public void setColor(String color) {this.color = color;}@Overridepublic String toString() {return "Car{" +"name='" + name + '\'' +", age=" + age +", color='" + color + '\'' +'}';}
}
編寫測(cè)試類
package com.atguigu.reflect;import org.junit.jupiter.api.Test;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;public class TestCar {//1、獲取Class對(duì)象多種方式@Testpublic void test01() throws Exception {//1 類名.classClass clazz1 = Car.class;//2 對(duì)象.getClass()Class clazz2 = new Car().getClass();//3 Class.forName("全路徑")Class clazz3 = Class.forName("com.atguigu.reflect.Car");//實(shí)例化Car car = (Car)clazz3.getConstructor().newInstance();System.out.println(car);}//2、獲取構(gòu)造方法@Testpublic void test02() throws Exception {Class clazz = Car.class;//獲取所有構(gòu)造// getConstructors()獲取所有public的構(gòu)造方法
// Constructor[] constructors = clazz.getConstructors();// getDeclaredConstructors()獲取所有的構(gòu)造方法public privateConstructor[] constructors = clazz.getDeclaredConstructors();for (Constructor c:constructors) {System.out.println("方法名稱："+c.getName()+" 參數(shù)個(gè)數(shù)："+c.getParameterCount());}//指定有參數(shù)構(gòu)造創(chuàng)建對(duì)象//1 構(gòu)造public
// Constructor c1 = clazz.getConstructor(String.class, int.class, String.class);
// Car car1 = (Car)c1.newInstance("夏利", 10, "紅色");
// System.out.println(car1);//2 構(gòu)造privateConstructor c2 = clazz.getDeclaredConstructor(String.class, int.class, String.class);c2.setAccessible(true);Car car2 = (Car)c2.newInstance("捷達(dá)", 15, "白色");System.out.println(car2);}//3、獲取屬性@Testpublic void test03() throws Exception {Class clazz = Car.class;Car car = (Car)clazz.getDeclaredConstructor().newInstance();//獲取所有public屬性//Field[] fields = clazz.getFields();//獲取所有屬性（包含私有屬性）Field[] fields = clazz.getDeclaredFields();for (Field field:fields) {if(field.getName().equals("name")) {//設(shè)置允許訪問(wèn)field.setAccessible(true);field.set(car,"五菱宏光");System.out.println(car);}System.out.println(field.getName());}}//4、獲取方法@Testpublic void test04() throws Exception {Car car = new Car("奔馳",10,"黑色");Class clazz = car.getClass();//1 public方法Method[] methods = clazz.getMethods();for (Method m1:methods) {//System.out.println(m1.getName());//執(zhí)行方法 toStringif(m1.getName().equals("toString")) {String invoke = (String)m1.invoke(car);//System.out.println("toString執(zhí)行了："+invoke);}}//2 private方法Method[] methodsAll = clazz.getDeclaredMethods();for (Method m:methodsAll) {//執(zhí)行方法 runif(m.getName().equals("run")) {m.setAccessible(true);m.invoke(car);}}}
}
4.2、實(shí)現(xiàn)Spring的IoC
我們知道，IoC（控制反轉(zhuǎn)）和DI（依賴注入）是Spring里面核心的東西，那么，我們?nèi)绾巫约菏謱懗鲞@樣的代碼呢？下面我們就一步一步寫出Spring框架最核心的部分。
①搭建子模塊
搭建模塊：guigu-spring，搭建方式如其他spring子模塊
②準(zhǔn)備測(cè)試需要的bean
添加依賴
<dependencies><!--junit5測(cè)試--><dependency><groupId>org.junit.jupiter</groupId><artifactId>junit-jupiter-api</artifactId><version>5.3.1</version></dependency>
</dependencies>
創(chuàng)建UserDao接口
package com.atguigu.spring6.test.dao;public interface UserDao {public void print();
}
創(chuàng)建UserDaoImpl實(shí)現(xiàn)
package com.atguigu.spring6.test.dao.impl;import com.atguigu.spring.dao.UserDao;public class UserDaoImpl implements UserDao {@Overridepublic void print() {System.out.println("Dao層執(zhí)行結(jié)束");}
}創(chuàng)建UserService接口
package com.atguigu.spring6.test.service;public interface UserService {public void out();
}
創(chuàng)建UserServiceImpl實(shí)現(xiàn)類
package com.atguigu.spring.test.service.impl;import com.atguigu.spring.core.annotation.Bean;
import com.atguigu.spring.service.UserService;@Bean
public class UserServiceImpl implements UserService {// private UserDao userDao;@Overridepublic void out() {//userDao.print();System.out.println("Service層執(zhí)行結(jié)束");}
}③定義注解
我們通過(guò)注解的形式加載bean與實(shí)現(xiàn)依賴注入
bean注解
package com.atguigu.spring.core.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Bean {
}
依賴注入注解
package com.atguigu.spring.core.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Di {
}
說(shuō)明：上面兩個(gè)注解可以隨意取名
④定義bean容器接口
package com.atguigu.spring.core;public interface ApplicationContext {Object getBean(Class clazz);
}
⑤編寫注解bean容器接口實(shí)現(xiàn)
AnnotationApplicationContext基于注解掃描bean
package com.atguigu.spring.core;import java.util.HashMap;public class AnnotationApplicationContext implements ApplicationContext {//存儲(chǔ)bean的容器private HashMap<Class, Object> beanFactory = new HashMap<>();@Overridepublic Object getBean(Class clazz) {return beanFactory.get(clazz);}/*** 根據(jù)包掃描加載bean* @param basePackage*/public AnnotationApplicationContext(String basePackage) {}
}
⑥編寫掃描bean邏輯
我們通過(guò)構(gòu)造方法傳入包的base路徑，掃描被@Bean注解的java對(duì)象，完整代碼如下：
package com.atguigu.spring.core;import com.atguigu.spring.core.annotation.Bean;import java.io.File;
import java.util.HashMap;public class AnnotationApplicationContext implements ApplicationContext {//存儲(chǔ)bean的容器private HashMap<Class, Object> beanFactory = new HashMap<>();private static String rootPath;@Overridepublic Object getBean(Class clazz) {return beanFactory.get(clazz);}/*** 根據(jù)包掃描加載bean* @param basePackage*/public AnnotationApplicationContext(String basePackage) {try {String packageDirName = basePackage.replaceAll("\\.", "\\\\");Enumeration<URL> dirs =Thread.currentThread().getContextClassLoader().getResources(packageDirName);while (dirs.hasMoreElements()) {URL url = dirs.nextElement();String filePath = URLDecoder.decode(url.getFile(),"utf-8");rootPath = filePath.substring(0, filePath.length()-packageDirName.length());loadBean(new File(filePath));}} catch (Exception e) {throw new RuntimeException(e);}}private void loadBean(File fileParent) {if (fileParent.isDirectory()) {File[] childrenFiles = fileParent.listFiles();if(childrenFiles == null || childrenFiles.length == 0){return;}for (File child : childrenFiles) {if (child.isDirectory()) {//如果是個(gè)文件夾就繼續(xù)調(diào)用該方法,使用了遞歸loadBean(child);} else {//通過(guò)文件路徑轉(zhuǎn)變成全類名,第一步把絕對(duì)路徑部分去掉String pathWithClass = child.getAbsolutePath().substring(rootPath.length() - 1);//選中class文件if (pathWithClass.contains(".class")) {// com.xinzhi.dao.UserDao//去掉.class后綴，并且把 \ 替換成 .String fullName = pathWithClass.replaceAll("\\\\", ".").replace(".class", "");try {Class<?> aClass = Class.forName(fullName);//把非接口的類實(shí)例化放在map中if(!aClass.isInterface()){Bean annotation = aClass.getAnnotation(Bean.class);if(annotation != null){Object instance = aClass.newInstance();//判斷一下有沒(méi)有接口if(aClass.getInterfaces().length > 0) {//如果有接口把接口的class當(dāng)成key，實(shí)例對(duì)象當(dāng)成valueSystem.out.println("正在加載【"+ aClass.getInterfaces()[0] +"】,實(shí)例對(duì)象是：" + instance.getClass().getName());beanFactory.put(aClass.getInterfaces()[0], instance);}else{//如果有接口把自己的class當(dāng)成key，實(shí)例對(duì)象當(dāng)成valueSystem.out.println("正在加載【"+ aClass.getName() +"】,實(shí)例對(duì)象是：" + instance.getClass().getName());beanFactory.put(aClass, instance);}}}} catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {e.printStackTrace();}}}}}}}
⑦java類標(biāo)識(shí)Bean注解
@Bean
public class UserServiceImpl implements UserService
@Bean
public class UserDaoImpl implements UserDao
⑧測(cè)試Bean加載
package com.atguigu.spring;import com.atguigu.spring.core.AnnotationApplicationContext;
import com.atguigu.spring.core.ApplicationContext;
import com.atguigu.spring.test.service.UserService;
import org.junit.jupiter.api.Test;public class SpringIocTest {@Testpublic void testIoc() {ApplicationContext applicationContext = new AnnotationApplicationContext("com.atguigu.spring.test");UserService userService = (UserService)applicationContext.getBean(UserService.class);userService.out();System.out.println("run success");}
}
控制臺(tái)打印測(cè)試
⑨依賴注入
只要userDao.print();調(diào)用成功，說(shuō)明就注入成功
package com.atguigu.spring.test.service.impl;import com.atguigu.spring.core.annotation.Bean;
import com.atguigu.spring.core.annotation.Di;
import com.atguigu.spring.dao.UserDao;
import com.atguigu.spring.service.UserService;@Bean
public class UserServiceImpl implements UserService {@Diprivate UserDao userDao;@Overridepublic void out() {userDao.print();System.out.println("Service層執(zhí)行結(jié)束");}
}
執(zhí)行第八步：報(bào)錯(cuò)了，說(shuō)明當(dāng)前userDao是個(gè)空對(duì)象
⑩依賴注入實(shí)現(xiàn)
package com.atguigu.spring.core;import com.atguigu.spring.core.annotation.Bean;
import com.atguigu.spring.core.annotation.Di;import java.io.File;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;public class AnnotationApplicationContext implements ApplicationContext {//存儲(chǔ)bean的容器private HashMap<Class, Object> beanFactory = new HashMap<>();private static String rootPath;@Overridepublic Object getBean(Class clazz) {return beanFactory.get(clazz);}/*** 根據(jù)包掃描加載bean* @param basePackage*/public AnnotationApplicationContext(String basePackage) {try {String packageDirName = basePackage.replaceAll("\\.", "\\\\");Enumeration<URL> dirs =Thread.currentThread().getContextClassLoader().getResources(packageDirName);while (dirs.hasMoreElements()) {URL url = dirs.nextElement();String filePath = URLDecoder.decode(url.getFile(),"utf-8");rootPath = filePath.substring(0, filePath.length()-packageDirName.length());loadBean(new File(filePath));}} catch (Exception e) {throw new RuntimeException(e);}//依賴注入loadDi();}private void loadBean(File fileParent) {if (fileParent.isDirectory()) {File[] childrenFiles = fileParent.listFiles();if(childrenFiles == null || childrenFiles.length == 0){return;}for (File child : childrenFiles) {if (child.isDirectory()) {//如果是個(gè)文件夾就繼續(xù)調(diào)用該方法,使用了遞歸loadBean(child);} else {//通過(guò)文件路徑轉(zhuǎn)變成全類名,第一步把絕對(duì)路徑部分去掉String pathWithClass = child.getAbsolutePath().substring(rootPath.length() - 1);//選中class文件if (pathWithClass.contains(".class")) {// com.xinzhi.dao.UserDao//去掉.class后綴，并且把 \ 替換成 .String fullName = pathWithClass.replaceAll("\\\\", ".").replace(".class", "");try {Class<?> aClass = Class.forName(fullName);//把非接口的類實(shí)例化放在map中if(!aClass.isInterface()){Bean annotation = aClass.getAnnotation(Bean.class);if(annotation != null){Object instance = aClass.newInstance();//判斷一下有沒(méi)有接口if(aClass.getInterfaces().length > 0) {//如果有接口把接口的class當(dāng)成key，實(shí)例對(duì)象當(dāng)成valueSystem.out.println("正在加載【"+ aClass.getInterfaces()[0] +"】,實(shí)例對(duì)象是：" + instance.getClass().getName());beanFactory.put(aClass.getInterfaces()[0], instance);}else{//如果有接口把自己的class當(dāng)成key，實(shí)例對(duì)象當(dāng)成valueSystem.out.println("正在加載【"+ aClass.getName() +"】,實(shí)例對(duì)象是：" + instance.getClass().getName());beanFactory.put(aClass, instance);}}}} catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {e.printStackTrace();}}}}}}private void loadDi() {for(Map.Entry<Class,Object> entry : beanFactory.entrySet()){//就是咱們放在容器的對(duì)象Object obj = entry.getValue();Class<?> aClass = obj.getClass();Field[] declaredFields = aClass.getDeclaredFields();for (Field field : declaredFields){Di annotation = field.getAnnotation(Di.class);if( annotation != null ){field.setAccessible(true);try {System.out.println("正在給【"+obj.getClass().getName()+"】屬性【" + field.getName() + "】注入值【"+ beanFactory.get(field.getType()).getClass().getName() +"】");field.set(obj,beanFactory.get(field.getType()));} catch (IllegalAccessException e) {e.printStackTrace();}}}}}}
執(zhí)行第八步：執(zhí)行成功，依賴注入成功