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修复一个线程安全问题，解决循环依赖问题 #1

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修复一个线程安全问题，解决循环依赖问题 #1

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d80598c
单例Bean创建时的一个线程安全问题
Ticsmyc May 25, 2021
5bce699
解决循环依赖问题
Ticsmyc May 25, 2021
3204367
fixbug：空指针
Ticsmyc Oct 14, 2021
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43 changes: 34 additions & 9 deletions src/main/java/top/guoziyang/springframework/factory/AbstractBeanFactory.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,26 +2,26 @@

import top.guoziyang.springframework.entity.BeanDefinition;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public abstract class AbstractBeanFactory implements BeanFactory {

ConcurrentHashMap<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>();

ThreadLocal<HashMap<String,Object>> earylyBean = new ThreadLocal<HashMap<String, Object>>();

@Override
public Object getBean(String name) throws Exception {
BeanDefinition beanDefinition = beanDefinitionMap.get(name);
if(beanDefinition == null) {
throw new RuntimeException("Unable to find the bean of this name, please check!");
}
if(!beanDefinition.isSingleton() || beanDefinition.getBean() == null) {
return doCreateBean(beanDefinition);
} else {
return doCreateBean(beanDefinition);
}
return getBeanFromBeanDefinition(beanDefinition);
}


@Override
public Object getBean(Class clazz) throws Exception {
BeanDefinition beanDefinition = null;
Expand All @@ -34,11 +34,36 @@ public Object getBean(Class clazz) throws Exception {
if(beanDefinition == null) {
throw new RuntimeException("Unable to find the bean of this class, please check!");
}
if(!beanDefinition.isSingleton() || beanDefinition.getBean() == null) {
return doCreateBean(beanDefinition);
} else {
return beanDefinition.getBean();
return getBeanFromBeanDefinition(beanDefinition);
}

private Object getBeanFromBeanDefinition(BeanDefinition beanDefinition) throws Exception {
if(beanDefinition.isSingleton()){
if(beanDefinition.getBean()!=null){
return beanDefinition.getBean();
}else{
/**
* bug场景 ：当多个线程使用同一个BeanFactory，针对同一个单例的beanDefinition 调用getBean
* 如果没有锁，会创建多个对象
*/
synchronized (this){
if(beanDefinition.getBean()==null){
return doCreateBean(beanDefinition);
}else{
return beanDefinition.getBean();
}
}
}
}else{
//不是单例 先从earlyBean中找，如果没有就新创建
HashMap<String, Object> earlyBeanMap = earylyBean.get();
if(earlyBeanMap!=null && earlyBeanMap.containsKey(beanDefinition.getBeanClassName())){
return earlyBeanMap.get(beanDefinition.getBeanClassName());
}else{
return doCreateBean(beanDefinition);
}
}

}

@Override
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42 changes: 31 additions & 11 deletions src/main/java/top/guoziyang/springframework/factory/AutowiredCapableBeanFactory.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
import top.guoziyang.springframework.entity.PropertyValue;

import java.lang.reflect.Field;
import java.util.HashMap;

public class AutowiredCapableBeanFactory extends AbstractBeanFactory {

Expand All @@ -15,6 +16,8 @@ Object doCreateBean(BeanDefinition beanDefinition) throws Exception {
}
Object bean = beanDefinition.getBeanClass().newInstance();
if(beanDefinition.isSingleton()) {
//如果是单例，就算没有完成属性赋值，也可以存起来
//这样可以直接避免出现循环依赖导致的死循环问题
beanDefinition.setBean(bean);
}
applyPropertyValues(bean, beanDefinition);
Expand All @@ -36,32 +39,49 @@ void applyPropertyValues(Object bean, BeanDefinition beanDefinition) throws Exce
// 优先按照自定义名称匹配
BeanDefinition refDefinition = beanDefinitionMap.get(beanReference.getName());
if(refDefinition != null) {
if(!refDefinition.isSingleton() || refDefinition.getBean() == null) {
value = doCreateBean(refDefinition);
} else {
value = refDefinition.getBean();
}
value = createBeanFromBeanDefinition(bean, beanDefinition, beanReference, refDefinition);
} else {
// 按照类型匹配，返回第一个匹配的
Class clazz = Class.forName(beanReference.getName());
for(BeanDefinition definition : beanDefinitionMap.values()) {
if(clazz.isAssignableFrom(definition.getBeanClass())) {
if(!definition.isSingleton() || definition.getBean() == null) {
value = doCreateBean(definition);
} else {
value = definition.getBean();
}
value = createBeanFromBeanDefinition(bean, beanDefinition, beanReference, definition);
}
}
}

}
if(value == null) {
throw new RuntimeException("无法注入");
}
field.setAccessible(true);
field.set(bean, value);
}
//如果自己在earlyBean里，就删除
if(earylyBean.get()!=null && earylyBean.get().containsKey(beanDefinition.getBeanClassName())){
earylyBean.get().remove(beanDefinition.getBeanClassName());
}
}

private Object createBeanFromBeanDefinition(Object bean, BeanDefinition beanDefinition, BeanReference beanReference,
BeanDefinition refDefinition) throws Exception {
if(refDefinition.isSingleton()){
//单例就直接拿
if(refDefinition.getBean()!=null){
return refDefinition.getBean();
}else{
return doCreateBean(refDefinition);
}
}else{
//先把自己放入earlyBean
if(earylyBean.get() == null){
earylyBean.set(new HashMap<>());
}
if(!earylyBean.get().containsKey(beanDefinition.getBeanClassName())){
earylyBean.get().put(beanDefinition.getBeanClassName(), bean);
}
//再尝试获取所需的Bean
return getBean(beanReference.getName());
}
}


Expand Down