1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18

public interface BeanFactory {
    // 从容器中根据beanname获取
	Object getBean(String name) throws BeansException;
    // 延迟加载对象
	<T> ObjectProvider<T> getBeanProvider(Class<T> requiredType);
    // 是否存在beanName
	boolean containsBean(String name);
    // 这个 beanName 是否是单例的. 映射成 bean
	boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
    // 是否多例.
	boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
    // 类型是否匹配
	boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;
    // 获取bean的类型
	Class<?> getType(String name) throws NoSuchBeanDefinitionException;
    // 获取别名
	String[] getAliases(String name);
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14

public class UserBean {

  private String name;
  private Integer age;

  public static UserBean createInstance() {
    UserBean userBean = new UserBean();
    userBean.setAge(18);
    userBean.setName("zhangsan");

    return userBean;
  }
    // get set 忽略
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13

public interface UserBeanFactory {
  UserBean factory();
}

public class UserBeanFactoryImpl implements
        UserBeanFactory {


    @Override
    public UserBean factory() {
        return UserBean.createInstance();
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17

public class UserFactoryBean implements FactoryBean<UserBean> {

  @Override
  public boolean isSingleton() {
    return true;
  }

  @Override
  public UserBean getObject() throws Exception {
    return UserBean.createInstance();
  }

  @Override
  public Class<?> getObjectType() {
    return UserBean.class;
  }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


   <!--  静态方法-->
   <bean id="static-method-user"
        class="org.source.hot.spring.overview.ioc.bean.init.UserBean"
        factory-method="createInstance"/>

   <!--  工厂方法创建-->
   <bean id="factory-use" class="org.source.hot.spring.overview.ioc.bean.init.UserBean"
        factory-bean="userFactory" factory-method="factory"></bean>
   <!--user 工厂bean-->
   <bean id="userFactory"
        class="org.source.hot.spring.overview.ioc.bean.init.UserBeanFactoryImpl"/>
   <!--factory bean-->
   <bean id="factory-bean-user"
        class="org.source.hot.spring.overview.ioc.bean.init.UserFactoryBean"/>

</beans>

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13

public class SpringBeanInstantiation {

  public static void main(String[] args) {
    BeanFactory context = new ClassPathXmlApplicationContext(
        "META-INF/beans/spring-bean-instantiation.xml");

    UserBean staticMethodBean = context.getBean("static-method-user", UserBean.class);
    UserBean factoryUser = context.getBean("factory-use", UserBean.class);
    UserBean factoryBean = context.getBean("factory-bean-user", UserBean.class);
    System.out.println();

  }
}

1

 UserBean staticMethodBean = context.getBean("static-method-user", UserBean.class);

1
2
3
4
5
6
7
8
9

@Override
	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
	    // 判断 beanFactory 是否存活
		assertBeanFactoryActive();

		// 1. 获取 beanFactory
        // 2. 根据 beanName + class 获取 Bean
		return getBeanFactory().getBean(name, requiredType);
	}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12

protected void assertBeanFactoryActive() {
        // 是否存活
        if (!this.active.get()) {
            // 是否关闭
            if (this.closed.get()) {
                throw new IllegalStateException(getDisplayName() + " has been closed already");
            }
            else {
                throw new IllegalStateException(getDisplayName() + " has not been refreshed yet");
            }
        }
    }

1
2
3
4
5
6

protected String transformedBeanName(String name) {
    // 转换 beanName .
    // 1. 通过·BeanFactoryUtils.transformedBeanName· 求beanName
    // 2. 如果是有别名的(方法参数是别名) . 会从别名列表中获取对应的 beanName
    return canonicalName(BeanFactoryUtils.transformedBeanName(name));
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

public static String transformedBeanName(String name) {
       Assert.notNull(name, "'name' must not be null");
       // 名字不是 & 开头直接返回
   if (!name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX)) {
      return name;
   }
   // 截取字符串 在返回
   return transformedBeanNameCache.computeIfAbsent(name, beanName -> {
      do {
         beanName = beanName.substring(BeanFactory.FACTORY_BEAN_PREFIX.length());
      }
      while (beanName.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
      return beanName;
   });
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14

public String canonicalName(String name) {
    String canonicalName = name;
    // Handle aliasing...
    String resolvedName;
    do {
        // 别名的获取
        resolvedName = this.aliasMap.get(canonicalName);
        if (resolvedName != null) {
            canonicalName = resolvedName;
        }
    }
    while (resolvedName != null);
    return canonicalName;
}

1

private final Map<String, String> aliasMap = new ConcurrentHashMap<>(16);

1
2
3
4

<bean id="factory-bean-user"
     class="org.source.hot.spring.overview.ioc.bean.init.UserFactoryBean"/>

<alias name="factory-bean-user" alias="userFactoryBean"/>

1
2
3
4
5

@Override
@Nullable
public Object getSingleton(String beanName) {
   return getSingleton(beanName, true);
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
    // 尝试从单例缓存中获取
    Object singletonObject = this.singletonObjects.get(beanName);
    // 单例对象是否null
    // 这个 beanName 是否正在创建
    if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
        // 锁
        synchronized (this.singletonObjects) {
            // 从延迟加载的map中获取
            singletonObject = this.earlySingletonObjects.get(beanName);
            // 对象是否空 ， 是否允许提前应用
            if (singletonObject == null && allowEarlyReference) {
                // 从对象工厂map中获取对象工厂
                ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                if (singletonFactory != null) {
                    // 对象获取后设置
                    singletonObject = singletonFactory.getObject();
                    this.earlySingletonObjects.put(beanName, singletonObject);
                    this.singletonFactories.remove(beanName);
                }
            }
        }
    }
    return singletonObject;
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

/**
 *  Cache of singleton objects: bean name to bean instance.
 *
 * 单例对象容器, key: beanName , value: bean实例
 * */
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);


    /**
     *  Cache of singleton factories: bean name to ObjectFactory.
     * key: beanName
     * value: 对象工厂
     * */
    private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);



    /**
     *  Names of beans that are currently in creation.
     *
     * 当前正在实例化的beanName
     *
     * */
    private final Set<String> singletonsCurrentlyInCreation =
            Collections.newSetFromMap(new ConcurrentHashMap<>(16));

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

protected Object getObjectForBeanInstance(
			Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {

		// Don't let calling code try to dereference the factory if the bean isn't a factory.
		// 判断 beanName 是不是 bean 工厂
		if (BeanFactoryUtils.isFactoryDereference(name)) {
			// 类型判断
			if (beanInstance instanceof NullBean) {
				return beanInstance;
			}
			if (!(beanInstance instanceof FactoryBean)) {
				throw new BeanIsNotAFactoryException(beanName, beanInstance.getClass());
			}
			if (mbd != null) {
				mbd.isFactoryBean = true;
			}
			// 返回实例
			return beanInstance;
		}

		// Now we have the bean instance, which may be a normal bean or a FactoryBean.
		// If it's a FactoryBean, we use it to create a bean instance, unless the
		// caller actually wants a reference to the factory.
		// 判断是否是 factoryBean
		if (!(beanInstance instanceof FactoryBean)) {
			return beanInstance;
		}

		Object object = null;
		if (mbd != null) {
			mbd.isFactoryBean = true;
		}
		else {
			// 缓存中获取
			object = getCachedObjectForFactoryBean(beanName);
		}
		if (object == null) {
			// Return bean instance from factory.
			// 如果还是 null 从 factory bean 中创建
			FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
			// Caches object obtained from FactoryBean if it is a singleton.
			if (mbd == null && containsBeanDefinition(beanName)) {
				mbd = getMergedLocalBeanDefinition(beanName);
			}
			boolean synthetic = (mbd != null && mbd.isSynthetic());
			// 从 FactoryBean 中获取bean实例
			object = getObjectFromFactoryBean(factory, beanName, !synthetic);
		}
		return object;
	}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64

	protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
		// 是否单例 是否已经包含
		if (factory.isSingleton() && containsSingleton(beanName)) {
			synchronized (getSingletonMutex()) {
				// 从工厂bean的缓存中获取
				Object object = this.factoryBeanObjectCache.get(beanName);
				if (object == null) {

					// 从 factoryBean 接口中获取
					object = doGetObjectFromFactoryBean(factory, beanName);
					// Only post-process and store if not put there already during getObject() call above
					// (e.g. because of circular reference processing triggered by custom getBean calls)
					// 从缓存map中获取
					Object alreadyThere = this.factoryBeanObjectCache.get(beanName);
					if (alreadyThere != null) {
						// 如果缓存中获取有值
						// object 覆盖
						object = alreadyThere;
					}
					else {
						if (shouldPostProcess) {
							if (isSingletonCurrentlyInCreation(beanName)) {
								// Temporarily return non-post-processed object, not storing it yet..
								return object;
							}
							// 单例创建前的验证
							beforeSingletonCreation(beanName);
							try {
								// 从 FactoryBean 接口创建的 后置处理
								object = postProcessObjectFromFactoryBean(object, beanName);
							}
							catch (Throwable ex) {
								throw new BeanCreationException(beanName,
										"Post-processing of FactoryBean's singleton object failed", ex);
							}
							finally {
								// 单例bean创建之后
								afterSingletonCreation(beanName);
							}
						}
						// 是否包含bean name
						if (containsSingleton(beanName)) {
							// 插入缓存
							// 后续使用的时候可以直接获取
							this.factoryBeanObjectCache.put(beanName, object);
						}
					}
				}
				return object;
			}
		}
		else {
			Object object = doGetObjectFromFactoryBean(factory, beanName);
			if (shouldPostProcess) {
				try {
					object = postProcessObjectFromFactoryBean(object, beanName);
				}
				catch (Throwable ex) {
					throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);
				}
			}
			return object;
		}
	}

1
2
3
4
5
6
7

protected void beforeSingletonCreation(String beanName) {
   // 排除的单例beanName 是否包含当前beanName
   // 添加当前正在初始化的beanName 是否正确
   if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName)) {
      throw new BeanCurrentlyInCreationException(beanName);
   }
}

1
2
3
4
5
6
7

protected void afterSingletonCreation(String beanName) {
   // 排除的单例beanName 是否包含当前beanName
   // 移除当前正在初始化的beanName 是否正确
   if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName)) {
      throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
   }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

	protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
			@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
		// 转换beanName
		final String beanName = transformedBeanName(name);
		Object bean;

		// Eagerly check singleton cache for manually registered singletons.
		// 获取单例对象
		Object sharedInstance = getSingleton(beanName);
		// 单例对象是否存在 参数是否为空
		if (sharedInstance != null && args == null) {
			if (logger.isTraceEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			// 实例化bean
			bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}

        // 省略后续内容
    }

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

else {
   // Fail if we're already creating this bean instance:
   // We're assumably within a circular reference.
   // 循环依赖的问题
   if (isPrototypeCurrentlyInCreation(beanName)) {
      throw new BeanCurrentlyInCreationException(beanName);
   }

   // Check if bean definition exists in this factory.
   BeanFactory parentBeanFactory = getParentBeanFactory();
   if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
      // Not found -> check parent.
      String nameToLookup = originalBeanName(name);
      if (parentBeanFactory instanceof AbstractBeanFactory) {
         return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
               nameToLookup, requiredType, args, typeCheckOnly);
      }
      else if (args != null) {
         // Delegation to parent with explicit args.
         return (T) parentBeanFactory.getBean(nameToLookup, args);
      }
      else if (requiredType != null) {
         // No args -> delegate to standard getBean method.
         return parentBeanFactory.getBean(nameToLookup, requiredType);
      }
      else {
         return (T) parentBeanFactory.getBean(nameToLookup);
      }
   }

1
2
3
4
5
6

protected void clearMergedBeanDefinition(String beanName) {
   RootBeanDefinition bd = this.mergedBeanDefinitions.get(beanName);
   if (bd != null) {
      bd.stale = true;
   }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17

protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
   // Quick check on the concurrent map first, with minimal locking.
   // 缓存中获取
   RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
   if (mbd != null && !mbd.stale) {
      return mbd;
   }
   // 合并的 bean 定义
   return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
}


	protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
			throws BeanDefinitionStoreException {

		return getMergedBeanDefinition(beanName, bd, null);
	}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

@Override
public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
   BeanDefinition bd = this.beanDefinitionMap.get(beanName);
   if (bd == null) {
      if (logger.isTraceEnabled()) {
         logger.trace("No bean named '" + beanName + "' found in " + this);
      }
      throw new NoSuchBeanDefinitionException(beanName);
   }
   return bd;
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

protected RootBeanDefinition getMergedBeanDefinition(
      String beanName, BeanDefinition bd, @Nullable BeanDefinition containingBd)
      throws BeanDefinitionStoreException {

   synchronized (this.mergedBeanDefinitions) {
      RootBeanDefinition mbd = null;
      RootBeanDefinition previous = null;

      // Check with full lock now in order to enforce the same merged instance.
      if (containingBd == null) {
         // 从缓存中获取
         mbd = this.mergedBeanDefinitions.get(beanName);
      }

      if (mbd == null || mbd.stale) {
         previous = mbd;
         // 是否存在父名称
         if (bd.getParentName() == null) {
            // Use copy of given root bean definition.
            // 类型是否等于RootBeanDefinition
            if (bd instanceof RootBeanDefinition) {
               // 做一次对象拷贝
               mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
            }
            else {
               // 将 beanDefinition 创建成 RootBeanDefinition
               mbd = new RootBeanDefinition(bd);
            }
         }

          // 省略其他
      }

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

{
					// Child bean definition: needs to be merged with parent.
					// 父BeanDefinition
					BeanDefinition pbd;
					try {
						// 父类beanName
						String parentBeanName = transformedBeanName(bd.getParentName());
						// 当前beanName是否等于父的beanName
						if (!beanName.equals(parentBeanName)) {
							// 存在父 beanName
							// 父 beanDefinition
							// 递归调用
							pbd = getMergedBeanDefinition(parentBeanName);
						}
						else {
							// 获取父 beanFactory
							BeanFactory parent = getParentBeanFactory();
							// beanFactory 类型判断
							if (parent instanceof ConfigurableBeanFactory) {
								// ConfigurableBeanFactory 的获取方式
								pbd = ((ConfigurableBeanFactory) parent).getMergedBeanDefinition(parentBeanName);
							}
							else {
								throw new NoSuchBeanDefinitionException(parentBeanName,
										"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +
												"': cannot be resolved without an AbstractBeanFactory parent");
							}
						}
					}
					catch (NoSuchBeanDefinitionException ex) {
						throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
								"Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
					}
					// Deep copy with overridden values.
					// 将 父 BeanDefinition 对象拷贝
					mbd = new RootBeanDefinition(pbd);
					// 覆盖 beanDefinition
					mbd.overrideFrom(bd);
				}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

   // Set default singleton scope, if not configured before.
   // 作用域设置
   if (!StringUtils.hasLength(mbd.getScope())) {
      // 没有设置作用域直接给单例类型
      mbd.setScope(SCOPE_SINGLETON);
   }

   // A bean contained in a non-singleton bean cannot be a singleton itself.
   // Let's correct this on the fly here, since this might be the result of
   // parent-child merging for the outer bean, in which case the original inner bean
   // definition will not have inherited the merged outer bean's singleton status.
   // 修正 作用域
   if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
      mbd.setScope(containingBd.getScope());
   }

   // Cache the merged bean definition for the time being
   // (it might still get re-merged later on in order to pick up metadata changes)
   if (containingBd == null && isCacheBeanMetadata()) {
      // 放入缓存
      this.mergedBeanDefinitions.put(beanName, mbd);
   }
}
if (previous != null) {
   copyRelevantMergedBeanDefinitionCaches(previous, mbd);
}
return mbd;

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19

// 需要依赖的bean
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
   for (String dep : dependsOn) {
      if (isDependent(beanName, dep)) {
         throw new BeanCreationException(mbd.getResourceDescription(), beanName,
               "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
      }
      // 注册依赖bean
      registerDependentBean(dep, beanName);
      try {
         getBean(dep);
      }
      catch (NoSuchBeanDefinitionException ex) {
         throw new BeanCreationException(mbd.getResourceDescription(), beanName,
               "'" + beanName + "' depends on missing bean '" + dep + "'", ex);
      }
   }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

private boolean isDependent(String beanName, String dependentBeanName, @Nullable Set<String> alreadySeen) {
   if (alreadySeen != null && alreadySeen.contains(beanName)) {
      return false;
   }
   // 别名
   String canonicalName = canonicalName(beanName);
   // 依赖列表中获取
   Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
   if (dependentBeans == null) {
      return false;
   }
   if (dependentBeans.contains(dependentBeanName)) {
      return true;
   }
   for (String transitiveDependency : dependentBeans) {
      if (alreadySeen == null) {
         alreadySeen = new HashSet<>();
      }
      alreadySeen.add(beanName);
      if (isDependent(transitiveDependency, dependentBeanName, alreadySeen)) {
         return true;
      }
   }
   return false;
}

1
2
3

<bean class="org.source.hot.spring.overview.ioc.bean.init.SystemUserBean" >
   <property name="userBean" ref="factory-use"/>
</bean>

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19

public void registerDependentBean(String beanName, String dependentBeanName) {
   // 别名
   String canonicalName = canonicalName(beanName);

   synchronized (this.dependentBeanMap) {
      // 向依赖关系中放入数据
      Set<String> dependentBeans =
            this.dependentBeanMap.computeIfAbsent(canonicalName, k -> new LinkedHashSet<>(8));
      if (!dependentBeans.add(dependentBeanName)) {
         return;
      }
   }

   synchronized (this.dependenciesForBeanMap) {
      Set<String> dependenciesForBean =
            this.dependenciesForBeanMap.computeIfAbsent(dependentBeanName, k -> new LinkedHashSet<>(8));
      dependenciesForBean.add(canonicalName);
   }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

if (mbd.isSingleton()) {
   sharedInstance = getSingleton(beanName, () -> {
      try {
         return createBean(beanName, mbd, args);
      }
      catch (BeansException ex) {
         // Explicitly remove instance from singleton cache: It might have been put there
         // eagerly by the creation process, to allow for circular reference resolution.
         // Also remove any beans that received a temporary reference to the bean.
         destroySingleton(beanName);
         throw ex;
      }
   });
   bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57

public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
   Assert.notNull(beanName, "Bean name must not be null");
   synchronized (this.singletonObjects) {
      // 从单例对象缓存中获取
      Object singletonObject = this.singletonObjects.get(beanName);
      if (singletonObject == null) {
         if (this.singletonsCurrentlyInDestruction) {
            throw new BeanCreationNotAllowedException(beanName,
                  "Singleton bean creation not allowed while singletons of this factory are in destruction " +
                        "(Do not request a bean from a BeanFactory in a destroy method implementation!)");
         }
         if (logger.isDebugEnabled()) {
            logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
         }
         // 单例创建前的验证
         beforeSingletonCreation(beanName);
         boolean newSingleton = false;
         boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
         if (recordSuppressedExceptions) {
            this.suppressedExceptions = new LinkedHashSet<>();
         }
         try {
            // 从 ObjectFactory 中获取
            singletonObject = singletonFactory.getObject();
            newSingleton = true;
         }
         catch (IllegalStateException ex) {
            // Has the singleton object implicitly appeared in the meantime ->
            // if yes, proceed with it since the exception indicates that state.
            singletonObject = this.singletonObjects.get(beanName);
            if (singletonObject == null) {
               throw ex;
            }
         }
         catch (BeanCreationException ex) {
            if (recordSuppressedExceptions) {
               for (Exception suppressedException : this.suppressedExceptions) {
                  ex.addRelatedCause(suppressedException);
               }
            }
            throw ex;
         }
         finally {
            if (recordSuppressedExceptions) {
               this.suppressedExceptions = null;
            }
            // 创建单例对象后的验证
            afterSingletonCreation(beanName);
         }
         if (newSingleton) {
            // 添加到 单例容器中
            addSingleton(beanName, singletonObject);
         }
      }
      return singletonObject;
   }
}

1
2
3

// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
Object beanInstance = doCreateBean(beanName, mbdToUse, args);

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21

@Nullable
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
   Object bean = null;
   if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
      // Make sure bean class is actually resolved at this point.
      if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
         Class<?> targetType = determineTargetType(beanName, mbd);
         if (targetType != null) {
            /**
             * 主要实现{@link org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation(java.lang.Class, java.lang.String)}
             */
            bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
            if (bean != null) {
               bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
            }
         }
      }
      mbd.beforeInstantiationResolved = (bean != null);
   }
   return bean;
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

		// Instantiate the bean.
		BeanWrapper instanceWrapper = null;
		if (mbd.isSingleton()) {
			// beanFactory 移除当前创建的beanName
			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
		}
		// beanWrapper 是否存在
		if (instanceWrapper == null) {
			// 创建 bean 实例
			instanceWrapper = createBeanInstance(beanName, mbd, args);
		}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
   // Make sure bean class is actually resolved at this point.
   // 获取 bean class
   Class<?> beanClass = resolveBeanClass(mbd, beanName);

   if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
      throw new BeanCreationException(mbd.getResourceDescription(), beanName,
            "Bean class isn't public, and non-public access not allowed: " + beanClass.getName()
      );
   }

   // 返回一个用来创建bean实例的回调接口
   // Supplier get 直接获取bean对象
   Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
   if (instanceSupplier != null) {
      return obtainFromSupplier(instanceSupplier, beanName);
   }

   if (mbd.getFactoryMethodName() != null) {
      // 通过工厂方法创建
      return instantiateUsingFactoryMethod(beanName, mbd, args);
   }

   // Shortcut when re-creating the same bean...
   boolean resolved = false;
   boolean autowireNecessary = false;
   if (args == null) {
      synchronized (mbd.constructorArgumentLock) {
         if (mbd.resolvedConstructorOrFactoryMethod != null) {
            resolved = true;
            autowireNecessary = mbd.constructorArgumentsResolved;
         }
      }
   }
   if (resolved) {
      if (autowireNecessary) {
         // 自动构造 bean
         return autowireConstructor(beanName, mbd, null, null);
      }
      else {
         // 实例化bean
         return instantiateBean(beanName, mbd);
      }
   }

   // Candidate constructors for autowiring?
   Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
   if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
         mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
      return autowireConstructor(beanName, mbd, ctors, args);
   }

   // Preferred constructors for default construction?
   ctors = mbd.getPreferredConstructors();
   if (ctors != null) {
      return autowireConstructor(beanName, mbd, ctors, null);
   }

   // No special handling: simply use no-arg constructor.
   return instantiateBean(beanName, mbd);
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

@Nullable
protected Class<?> resolveBeanClass(final RootBeanDefinition mbd, String beanName, final Class<?>... typesToMatch)
      throws CannotLoadBeanClassException {

   try {
      // 是否包含 bean 类型
      if (mbd.hasBeanClass()) {
         // 直接返回
         return mbd.getBeanClass();
      }
      if (System.getSecurityManager() != null) {
         return AccessController.doPrivileged((PrivilegedExceptionAction<Class<?>>) () ->
               doResolveBeanClass(mbd, typesToMatch), getAccessControlContext());
      }
      else {
         // 从 bean definition 中获取
         return doResolveBeanClass(mbd, typesToMatch);
      }
   }
   catch (PrivilegedActionException pae) {
      ClassNotFoundException ex = (ClassNotFoundException) pae.getException();
      throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
   }
   catch (ClassNotFoundException ex) {
      throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
   }
   catch (LinkageError err) {
      throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
   }
}