一、分析

IOC是Inversion of Control（控制反转）的缩写。它是一种软件设计原则，用于解耦组件之间的依赖关系。

也就是依赖对象的获取被反转了，从原来我们自己创建对象-》从IOC容器中获取，由它来管理。

这样的好处是什么？

代码更加简洁，不用自己去new对象
面向接口编程：解耦，易扩展，替换实现类；方便进行AOP编程

那么，你有啥思路？

其实可以这么理解，IOC容器=Bean工厂，Beanfactory会对外提供bean实例，所以需要提供getBean()方法；那么你要什么样的Bean，得描述告诉Bean工厂吧，所以需要一个Bean定义信息BeanDefinition，告诉它应该创建什么对象；我们定义的这些BeanDefinition存在哪？就需要一个注册器BeanDefinitionRegistry去维护这些信息

二、实现

1、版本1：实现Bean注入IOC容器，并从容器中获取

1）定义BeanDefinition

描述我们的bean是要单例还是多例，是通过什么去创建（直接new，还是通过工厂类创建），初始化以及销毁方法

import com.baomidou.mybatisplus.core.toolkit.StringUtils;/*** bean定义接口*/
public interface BeanDefinition {String SCOPE_SINGLETON = "singleton";String SCOPE_PROTOTYPE = "prototype";/*** 类*/Class<?> getBeanClass();void setBeanClass(Class<?> beanClass);/*** Scope*/void setScope(String scope);String getScope();/*** 是否单例*/boolean isSingleton();/*** 是否原型*/boolean isPrototype();/*** 工厂bean名*/String getFactoryBeanName();void setFactoryBeanName(String factoryBeanName);/*** 工厂方法名*/String getFactoryMethodName();void setFactoryMethodName(String factoryMethodName);/*** 初始化方法*/String getInitMethodName();void setInitMethodName(String initMethodName);/*** 销毁方法*/String getDestroyMethodName();void setDestroyMethodName(String destroyMethodName);/*** 是否为主要自动候选对象*/boolean isPrimary();void setPrimary(boolean primary);/*** 校验bean定义的合法性，BeanClass和FactoryMethodName只能存在一个，定义了FactoryMethodName，必须指定FactoryMethodName*/default boolean validate() {// 没定义类if (this.getBeanClass() == null) {// 工厂bean或工厂方法都没定义，则不合法if (StringUtils.isBlank(getFactoryBeanName()) || StringUtils.isBlank(getFactoryMethodName())) {return false;}}// 定义了类，又定义工厂bean，不合法if (this.getBeanClass() != null && StringUtils.isNotBlank(getFactoryBeanName())) {return false;}return true;}}

2）定义BeanDefinition实现类

定义一个通用实现类，实现BeanDefinition接口，对值的设置和获取

public class GenericBeanDefinition implements BeanDefinition {public static final String SCOPE_DEFAULT = "";private Class<?> beanClass;private String scope = SCOPE_DEFAULT;private String factoryBeanName;private String factoryMethodName;private String initMethodName;private String destroyMethodName;private boolean primary;@Overridepublic Class<?> getBeanClass() {return beanClass;}@Overridepublic void setBeanClass(Class<?> beanClass) {this.beanClass = beanClass;}@Overridepublic String getScope() {return scope;}@Overridepublic void setScope(String scope) {this.scope = scope;}/*** 默认是单例*/@Overridepublic boolean isSingleton() {return SCOPE_SINGLETON.equals(this.scope) || SCOPE_DEFAULT.equals(this.scope);}@Overridepublic boolean isPrototype() {return SCOPE_PROTOTYPE.equals(this.scope);}@Overridepublic String getFactoryBeanName() {return factoryBeanName;}@Overridepublic void setFactoryBeanName(String factoryBeanName) {this.factoryBeanName = factoryBeanName;}@Overridepublic String getFactoryMethodName() {return factoryMethodName;}@Overridepublic void setFactoryMethodName(String factoryMethodName) {this.factoryMethodName = factoryMethodName;}@Overridepublic String getInitMethodName() {return initMethodName;}@Overridepublic void setInitMethodName(String initMethodName) {this.initMethodName = initMethodName;}@Overridepublic String getDestroyMethodName() {return destroyMethodName;}@Overridepublic void setDestroyMethodName(String destroyMethodName) {this.destroyMethodName = destroyMethodName;}@Overridepublic boolean isPrimary() {return primary;}@Overridepublic void setPrimary(boolean primary) {this.primary = primary;}
}

3）定义BeanDefinitionRegistry

public interface BeanDefinitionRegistry {void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws Exception;BeanDefinition getBeanDefinition(String beanName);boolean containsBeanDefinition(String beanName);
}

4）定义Beanfactory

提供getBean方法，方便外部获取bean

public interface Beanfactory {Object getBean(String name) throws Exception;
}

5）定义默认Beanfactory实现类

实现BeanDefinitionRegistry和Beanfactory 接口，定义一个存储存储结构，存beanName和beanDefinition的映射关系；重写registerBeanDefinition和getBean等方法，定义了三种创建对象的方式：

• 直接new：new BeanClass
• 工厂静态方法：BeanClass.factoryMethodName()
• 工厂bean对象调用方法：new FactoryBeanName().factoryMethodName()

import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;@Slf4j
public class DefaultBeanFactory implements BeanDefinitionRegistry, Beanfactory {// 存储结构：存beanName和beanDefinition的映射关系protected Map<String, BeanDefinition> beanDefintionMap = new ConcurrentHashMap<>(256);@Overridepublic void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws Exception {Objects.requireNonNull(beanName, "注册bean需要提供beanName");Objects.requireNonNull(beanDefinition, "注册bean需要提供beanDefinition");// 校验给入的bean是否合法if (!beanDefinition.validate()) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义不合法：" + beanDefinition);}// Spring中默认是不可覆盖（抛异常），可通过参数 spring.main.allow-bean-definition-overriding: true 来允许覆盖if (this.containsBeanDefinition(beanName)) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义已存在:" + this.getBeanDefinition(beanName));}beanDefintionMap.put(beanName, beanDefinition);}@Overridepublic BeanDefinition getBeanDefinition(String beanName) {return beanDefintionMap.get(beanName);}@Overridepublic boolean containsBeanDefinition(String beanName) {return beanDefintionMap.containsKey(beanName);}@Overridepublic Object getBean(String name) throws Exception {return this.doGetBean(name);}private Object doGetBean(String beanName) throws Exception {Objects.requireNonNull(beanName, "beanName不能为空");BeanDefinition bd = this.getBeanDefinition(beanName);Objects.requireNonNull(bd, "beanDefinition不能为空");Object instance = doCreateInstance(bd);return instance;}private Object doCreateInstance(BeanDefinition bd) throws Exception {Class<?> beanClass = bd.getBeanClass();Object instance = null;if (beanClass != null) {if (StringUtils.isBlank(bd.getFactoryMethodName())) {// 构造方法来构造对象instance = this.createInstanceByConstructor(bd);} else {// 静态工厂方法instance = this.createInstanceByStaticFactoryMethod(bd);}} else {// 工厂bean方式来构造对象instance = this.createInstanceByFactoryBean(bd);}// 执行初始化方法this.doInit(bd, instance);return instance;}// 构造方法来构造对象：new BeanClass()private Object createInstanceByConstructor(BeanDefinition bd) throws Exception {try {Class<?> beanClass = bd.getBeanClass();return beanClass.newInstance();} catch (SecurityException e) {log.error("创建bean的实例异常,beanDefinition：" + bd, e);throw e;}}// 静态工厂方法：BeanClass.factoryMethodName()private Object createInstanceByStaticFactoryMethod(BeanDefinition bd) throws Exception {Class<?> beanClass = bd.getBeanClass();Method m = beanClass.getMethod(bd.getFactoryMethodName(), null);return m.invoke(beanClass, null);}// 工厂bean方式来构造对象：new FactoryBeanName().factoryMethodName()private Object createInstanceByFactoryBean(BeanDefinition bd) throws Exception {Object factoryBean = this.doGetBean(bd.getFactoryBeanName());Class<?> factoryBeanClass = factoryBean.getClass();Method m = factoryBeanClass.getMethod(bd.getFactoryMethodName(), null);return m.invoke(factoryBean, null);}private void doInit(BeanDefinition bd, Object instance) throws Exception {// 执行初始化方法if (StringUtils.isNotBlank(bd.getInitMethodName())) {Method m = instance.getClass().getMethod(bd.getInitMethodName(), null);m.invoke(instance, null);}}
}

2、版本2：新增工厂关闭方法和支持单例bean

主要调整DefaultBeanFactory，实现了Closeable，重写了close方法，只针对单例Bean做了销毁处理，原型不用去销毁
，不知道会创建多少个对象，也得不到这些对象，不用去管，调整doGetBean方法支持单例模式。

import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;
import java.io.Closeable;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;@Slf4j
public class DefaultBeanFactory implements BeanDefinitionRegistry, Beanfactory, Closeable {// 单例存储结构：存beanName和对应实例的映射关系private Map<String, Object> singletonBeanMap = new ConcurrentHashMap<>(256);// 省去其它代码...private Object doGetBean(String beanName) throws Exception {Objects.requireNonNull(beanName, "beanName不能为空");Object instance = singletonBeanMap.get(beanName);if (instance != null) {return instance;}BeanDefinition beanDefinition = this.getBeanDefinition(beanName);Objects.requireNonNull(beanDefinition, "beanDefinition不能为空");if (beanDefinition.isSingleton()) {synchronized (singletonBeanMap) {instance = singletonBeanMap.get(beanName);if (instance == null) {instance = doCreateInstance(beanDefinition);singletonBeanMap.put(beanName, instance);}}} else {instance = doCreateInstance(beanDefinition);}return instance;}@Overridepublic void close() {for (Map.Entry<String, BeanDefinition> beanDefinitionEntry : beanDefintionMap.entrySet()) {String beanName = beanDefinitionEntry.getKey();BeanDefinition beanDefinition = beanDefinitionEntry.getValue();if (beanDefinition.isSingleton() && singletonBeanMap.containsKey(beanName)) {Object instance = this.singletonBeanMap.get(beanName);try {Method m = instance.getClass().getMethod(beanDefinition.getDestroyMethodName(), null);m.invoke(instance, null);} catch (Exception e) {log.error("执行名字为[" + beanName + "] 的bean销毁方法异常", e);}}}}
}

额外扩展：实现一个预构建BeanFactory，可以在系统启动时，提前初始化

import lombok.extern.slf4j.Slf4j;
import java.util.Map;@Slf4j
public class PreBuildBeanFactory extends DefaultBeanFactory{public void preInstantiateSingletons() throws Exception {synchronized (this.beanDefintionMap) {for (Map.Entry<String, BeanDefinition> entry : this.beanDefintionMap.entrySet()) {String name = entry.getKey();BeanDefinition beanDefinition = entry.getValue();if (beanDefinition.isSingleton()) {this.getBean(name);if (log.isDebugEnabled()) {log.debug("preInstantiate: name=" + name + " " + beanDefinition);}}}}}
}

3、版本3：支持获取指定名字的类型

主要调整Beanfactory和DefaultBeanFactory，Beanfactory新增一个getType方法，让子类去实现

public interface Beanfactory {Class<?> getType(String name) throws Exception;
}

重写getType方法

@Slf4j
public class DefaultBeanFactory implements BeanDefinitionRegistry, Beanfactory, Closeable {@Overridepublic Class<?> getType(String name) throws Exception {BeanDefinition beanDefinition = this.getBeanDefinition(name);Class<?> beanClass = beanDefinition.getBeanClass();if (beanClass != null) {// 如果是静态工厂方法，需要获取工厂创建的对象if (StringUtils.isNotBlank(beanDefinition.getFactoryMethodName())) {return beanClass.getDeclaredMethod(beanDefinition.getFactoryMethodName(), null).getReturnType();} else {return beanClass;}} else {// 其它情况是工厂方法的处理beanClass = getType(beanDefinition.getFactoryBeanName());return beanClass.getDeclaredMethod(beanDefinition.getFactoryMethodName(), null).getReturnType();}}@Overridepublic BeanDefinition getBeanDefinition(String beanName) {return beanDefintionMap.get(beanName);}
}

4、版本4：获取指定类型的所有bean以及唯一bean

一个type可能对应多个name，使用的存储结构如下：

private Map<Class<?>, Set<String>> typeNameMap = new ConcurrentHashMap<>(256);

调整DefaultBeanFactory的registerBeanDefinition，新增registerTypeNameMap方法，实现映射类型和beanName集合，支持当前类，父类，以及实现的接口，在Spring中，当你注入一个子类时，它会自动注入该子类实现的接口，而不会自动注入其继承的父类。所以下面实现的registerSuperClassTypeNaemMap，是注入其继承的父类，可以选择不要。

@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws Exception {Objects.requireNonNull(beanName, "注册bean需要提供beanName");Objects.requireNonNull(beanDefinition, "注册bean需要提供beanDefinition");// 校验给入的bean是否合法if (!beanDefinition.validate()) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义不合法：" + beanDefinition);}// Spring中默认是不可覆盖（抛异常），可通过参数 spring.main.allow-bean-definition-overriding: true 来允许覆盖if (this.containsBeanDefinition(beanName)) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义已存在:" + this.getBeanDefinition(beanName));}beanDefintionMap.put(beanName, beanDefinition);registerTypeNameMap();
}public void registerTypeNameMap() throws Exception {for (String name : beanDefintionMap.keySet()) {Class<?> type = this.getType(name);// 注册本类this.registerTypeNameMap(type, name);// 注册父类this.registerSuperClassTypeNaemMap(type, name);// 注册实现的接口this.registerInterfaceTypeNaemMap(type, name);}}private void registerTypeNameMap(Class<?> type, String name) {Set<String> beanNames = typeNameMap.get(type);if (beanNames == null) {beanNames = new HashSet<>();typeNameMap.put(type, beanNames);}beanNames.add(name);}private void registerSuperClassTypeNaemMap(Class<?> type, String name) {Class<?> superclass = type.getSuperclass();if (superclass != null && !superclass.equals(Object.class)) {// 注册本类this.registerTypeNameMap(superclass, name);// 注册父类this.registerSuperClassTypeNaemMap(superclass, name);// 注册实现的接口this.registerInterfaceTypeNaemMap(superclass, name);}}private void registerInterfaceTypeNaemMap(Class<?> type, String name) {Class<?>[] interfaces = type.getInterfaces();for (Class<?> anInterface : interfaces) {this.registerTypeNameMap(anInterface, name);this.registerInterfaceTypeNaemMap(anInterface, name);}
}

Beanfactory新增两个方法如下：

public interface Beanfactory {<T> T getBean(Class<T> requiredType) throws Exception;<T> Map<String,T> getBeansOfType(Class<T> type)throws Exception;
}

DefaultBeanFactory 实现如下：

@Override
public <T> T getBean(Class<T> requiredType) throws Exception {Set<String> beanNames = typeNameMap.get(requiredType);if (null == beanNames) {return null;}if (beanNames.size() == 1) {String beanName = beanNames.iterator().next();return (T) this.getBean(beanName);} else {String primaryBeanName = null;for (String beanName : beanNames) {BeanDefinition beanDefinition = this.getBeanDefinition(beanName);if (beanDefinition != null && beanDefinition.isPrimary()) {if (primaryBeanName == null) {primaryBeanName = beanName;} else {throw new RuntimeException(requiredType + "类存在多个Primary，无法确定唯一一个Bean");}}}if (primaryBeanName != null) {return (T) this.getBean(primaryBeanName);} else {throw new RuntimeException(requiredType + "类未找到对应的Bean");}}
}@Override
public <T> Map<String, T> getBeansOfType(Class<T> type) throws Exception {Set<String> beanNames = typeNameMap.get(type);if (null == beanNames) {return null;}Map<String, T> nameBeanMap = new HashMap<String, T>();for (String beanName : beanNames) {nameBeanMap.put(beanName, (T) this.getBean(beanName));}return nameBeanMap;
}

5、版本5：支持Bean别名

待实现

三、最终完整版本

BeanDefinition

import com.baomidou.mybatisplus.core.toolkit.StringUtils;/*** bean定义接口*/
public interface BeanDefinition {String SCOPE_SINGLETON = "singleton";String SCOPE_PROTOTYPE = "prototype";/*** 类*/Class<?> getBeanClass();void setBeanClass(Class<?> beanClass);/*** Scope*/void setScope(String scope);String getScope();/*** 是否单例*/boolean isSingleton();/*** 是否原型*/boolean isPrototype();/*** 工厂bean名*/String getFactoryBeanName();void setFactoryBeanName(String factoryBeanName);/*** 工厂方法名*/String getFactoryMethodName();void setFactoryMethodName(String factoryMethodName);/*** 初始化方法*/String getInitMethodName();void setInitMethodName(String initMethodName);/*** 销毁方法*/String getDestroyMethodName();void setDestroyMethodName(String destroyMethodName);/*** 是否为主要自动候选对象*/boolean isPrimary();void setPrimary(boolean primary);/*** 校验bean定义的合法性，BeanClass和FactoryMethodName只能存在一个，定义了FactoryMethodName，必须指定FactoryMethodName*/default boolean validate() {// 没定义类if (this.getBeanClass() == null) {// 工厂bean或工厂方法都没定义，则不合法if (StringUtils.isBlank(getFactoryBeanName()) || StringUtils.isBlank(getFactoryMethodName())) {return false;}}// 定义了类，又定义工厂bean，不合法if (this.getBeanClass() != null && StringUtils.isNotBlank(getFactoryBeanName())) {return false;}return true;}}

GenericBeanDefinition

public class GenericBeanDefinition implements BeanDefinition {public static final String SCOPE_DEFAULT = "";private Class<?> beanClass;private String scope = SCOPE_DEFAULT;private String factoryBeanName;private String factoryMethodName;private String initMethodName;private String destroyMethodName;private boolean primary;@Overridepublic Class<?> getBeanClass() {return beanClass;}@Overridepublic void setBeanClass(Class<?> beanClass) {this.beanClass = beanClass;}@Overridepublic String getScope() {return scope;}@Overridepublic void setScope(String scope) {this.scope = scope;}/*** 默认是单例*/@Overridepublic boolean isSingleton() {return SCOPE_SINGLETON.equals(this.scope) || SCOPE_DEFAULT.equals(this.scope);}@Overridepublic boolean isPrototype() {return SCOPE_PROTOTYPE.equals(this.scope);}@Overridepublic String getFactoryBeanName() {return factoryBeanName;}@Overridepublic void setFactoryBeanName(String factoryBeanName) {this.factoryBeanName = factoryBeanName;}@Overridepublic String getFactoryMethodName() {return factoryMethodName;}@Overridepublic void setFactoryMethodName(String factoryMethodName) {this.factoryMethodName = factoryMethodName;}@Overridepublic String getInitMethodName() {return initMethodName;}@Overridepublic void setInitMethodName(String initMethodName) {this.initMethodName = initMethodName;}@Overridepublic String getDestroyMethodName() {return destroyMethodName;}@Overridepublic void setDestroyMethodName(String destroyMethodName) {this.destroyMethodName = destroyMethodName;}@Overridepublic boolean isPrimary() {return primary;}@Overridepublic void setPrimary(boolean primary) {this.primary = primary;}
}

BeanDefinitionRegistry

public interface BeanDefinitionRegistry {void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws Exception;BeanDefinition getBeanDefinition(String beanName);boolean containsBeanDefinition(String beanName);
}

Beanfactory

import java.util.Map;public interface Beanfactory {Object getBean(String name) throws Exception;Class<?> getType(String name) throws Exception;<T> T getBean(Class<T> requiredType) throws Exception;<T> Map<String,T> getBeansOfType(Class<T> type)throws Exception;
}

DefaultBeanFactory

import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;import java.io.Closeable;
import java.lang.reflect.Method;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;@Slf4j
public class DefaultBeanFactory implements BeanDefinitionRegistry, Beanfactory, Closeable {// 存储结构：存beanName和beanDefinition的映射关系protected Map<String, BeanDefinition> beanDefintionMap = new ConcurrentHashMap<>(256);private Map<String, Object> singletonBeanMap = new ConcurrentHashMap<>(256);private Map<Class<?>, Set<String>> typeNameMap = new ConcurrentHashMap<>(256);@Overridepublic void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws Exception {Objects.requireNonNull(beanName, "注册bean需要提供beanName");Objects.requireNonNull(beanDefinition, "注册bean需要提供beanDefinition");// 校验给入的bean是否合法if (!beanDefinition.validate()) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义不合法：" + beanDefinition);}// Spring中默认是不可覆盖（抛异常），可通过参数 spring.main.allow-bean-definition-overriding: true 来允许覆盖if (this.containsBeanDefinition(beanName)) {throw new RuntimeException("名字为[" + beanName + "] 的bean定义已存在:" + this.getBeanDefinition(beanName));}beanDefintionMap.put(beanName, beanDefinition);registerTypeNameMap();}public void registerTypeNameMap() throws Exception {for (String name : beanDefintionMap.keySet()) {Class<?> type = this.getType(name);// 注册本类this.registerTypeNameMap(type, name);// 注册父类：Spring不支持，我们这里也模拟注释掉，不开放// this.registerSuperClassTypeNaemMap(type, name);// 注册实现的接口this.registerInterfaceTypeNaemMap(type, name);}}private void registerTypeNameMap(Class<?> type, String name) {Set<String> beanNames = typeNameMap.get(type);if (beanNames == null) {beanNames = new HashSet<>();typeNameMap.put(type, beanNames);}beanNames.add(name);}private void registerSuperClassTypeNaemMap(Class<?> type, String name) {Class<?> superclass = type.getSuperclass();if (superclass != null && !superclass.equals(Object.class)) {// 注册本类this.registerTypeNameMap(superclass, name);// 注册父类this.registerSuperClassTypeNaemMap(superclass, name);// 注册实现的接口this.registerInterfaceTypeNaemMap(superclass, name);}}private void registerInterfaceTypeNaemMap(Class<?> type, String name) {Class<?>[] interfaces = type.getInterfaces();for (Class<?> anInterface : interfaces) {this.registerTypeNameMap(anInterface, name);this.registerInterfaceTypeNaemMap(anInterface, name);}}@Overridepublic BeanDefinition getBeanDefinition(String beanName) {return beanDefintionMap.get(beanName);}@Overridepublic boolean containsBeanDefinition(String beanName) {return beanDefintionMap.containsKey(beanName);}@Overridepublic Object getBean(String name) throws Exception {return this.doGetBean(name);}@Overridepublic Class<?> getType(String name) throws Exception {BeanDefinition beanDefinition = this.getBeanDefinition(name);Class<?> beanClass = beanDefinition.getBeanClass();if (beanClass != null) {// 如果是静态工厂方法，需要获取工厂创建的对象if (StringUtils.isNotBlank(beanDefinition.getFactoryMethodName())) {return beanClass.getDeclaredMethod(beanDefinition.getFactoryMethodName(), null).getReturnType();} else {return beanClass;}} else {// 其它情况是工厂方法的处理beanClass = getType(beanDefinition.getFactoryBeanName());return beanClass.getDeclaredMethod(beanDefinition.getFactoryMethodName(), null).getReturnType();}}@Overridepublic <T> T getBean(Class<T> requiredType) throws Exception {Set<String> beanNames = typeNameMap.get(requiredType);if (null == beanNames) {return null;}if (beanNames.size() == 1) {String beanName = beanNames.iterator().next();return (T) this.getBean(beanName);} else {String primaryBeanName = null;for (String beanName : beanNames) {BeanDefinition beanDefinition = this.getBeanDefinition(beanName);if (beanDefinition != null && beanDefinition.isPrimary()) {if (primaryBeanName == null) {primaryBeanName = beanName;} else {throw new RuntimeException(requiredType + "类存在多个Primary，无法确定唯一一个Bean");}}}if (primaryBeanName != null) {return (T) this.getBean(primaryBeanName);} else {throw new RuntimeException(requiredType + "类未找到对应的Bean");}}}@Overridepublic <T> Map<String, T> getBeansOfType(Class<T> type) throws Exception {Set<String> beanNames = typeNameMap.get(type);if (null == beanNames) {return null;}Map<String, T> nameBeanMap = new HashMap<String, T>();for (String beanName : beanNames) {nameBeanMap.put(beanName, (T) this.getBean(beanName));}return nameBeanMap;}private Object doGetBean(String beanName) throws Exception {Objects.requireNonNull(beanName, "beanName不能为空");Object instance = singletonBeanMap.get(beanName);if (instance != null) {return instance;}BeanDefinition beanDefinition = this.getBeanDefinition(beanName);Objects.requireNonNull(beanDefinition, "beanDefinition不能为空");if (beanDefinition.isSingleton()) {synchronized (singletonBeanMap) {instance = singletonBeanMap.get(beanName);if (instance == null) {instance = doCreateInstance(beanDefinition);singletonBeanMap.put(beanName, instance);}}} else {instance = doCreateInstance(beanDefinition);}return instance;}private Object doCreateInstance(BeanDefinition bd) throws Exception {Class<?> beanClass = bd.getBeanClass();Object instance = null;if (beanClass != null) {if (StringUtils.isBlank(bd.getFactoryMethodName())) {// 构造方法来构造对象instance = this.createInstanceByConstructor(bd);} else {// 静态工厂方法instance = this.createInstanceByStaticFactoryMethod(bd);}} else {// 工厂bean方式来构造对象instance = this.createInstanceByFactoryBean(bd);}// 执行初始化方法this.doInit(bd, instance);return instance;}// 构造方法来构造对象：new BeanClass()private Object createInstanceByConstructor(BeanDefinition bd) throws Exception {try {Class<?> beanClass = bd.getBeanClass();return beanClass.newInstance();} catch (SecurityException e) {log.error("创建bean的实例异常,beanDefinition：" + bd, e);throw e;}}// 静态工厂方法：BeanClass.factoryMethodName()private Object createInstanceByStaticFactoryMethod(BeanDefinition bd) throws Exception {Class<?> beanClass = bd.getBeanClass();Method m = beanClass.getMethod(bd.getFactoryMethodName(), null);return m.invoke(beanClass, null);}// 工厂bean方式来构造对象：new FactoryBeanName().factoryMethodName()private Object createInstanceByFactoryBean(BeanDefinition bd) throws Exception {Object factoryBean = this.doGetBean(bd.getFactoryBeanName());Class<?> factoryBeanClass = factoryBean.getClass();Method m = factoryBeanClass.getMethod(bd.getFactoryMethodName(), null);return m.invoke(factoryBean, null);}private void doInit(BeanDefinition bd, Object instance) throws Exception {// 执行初始化方法if (StringUtils.isNotBlank(bd.getInitMethodName())) {Method m = instance.getClass().getMethod(bd.getInitMethodName(), null);m.invoke(instance, null);}}@Overridepublic void close() {for (Map.Entry<String, BeanDefinition> beanDefinitionEntry : beanDefintionMap.entrySet()) {String beanName = beanDefinitionEntry.getKey();BeanDefinition beanDefinition = beanDefinitionEntry.getValue();if (beanDefinition.isSingleton() && singletonBeanMap.containsKey(beanName)) {Object instance = this.singletonBeanMap.get(beanName);try {Method m = instance.getClass().getMethod(beanDefinition.getDestroyMethodName(), null);m.invoke(instance, null);} catch (Exception e) {log.error("执行名字为[" + beanName + "] 的bean销毁方法异常", e);}}}}
}

PreBuildBeanFactory

import lombok.extern.slf4j.Slf4j;
import java.util.Map;@Slf4j
public class PreBuildBeanFactory extends DefaultBeanFactory{public void preInstantiateSingletons() throws Exception {synchronized (this.beanDefintionMap) {for (Map.Entry<String, BeanDefinition> entry : this.beanDefintionMap.entrySet()) {String name = entry.getKey();BeanDefinition beanDefinition = entry.getValue();if (beanDefinition.isSingleton()) {this.getBean(name);if (log.isDebugEnabled()) {log.debug("preInstantiate: name=" + name + " " + beanDefinition);}}}}}
}