注意，看完这篇文章需要很长很长很长时间。。。

本篇文章是SpringIOC源码解析（上）的续集，上一篇文章介绍了使用XML的方式启动Spring，然后追踪了BeanFactory容器的创建、配置文件的解析、Bean的注册等。

12. finishBeanFactoryInitialization()

前方超长篇幅预警。。。

刚才我们提到了bean还没有初始化。这个方法就是负责初始化所有的没有设置懒加载的singleton bean

开始撸了

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
 
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {

		if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
				beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
			beanFactory.setConversionService(
					beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
		}

		if (!beanFactory.hasEmbeddedValueResolver()) {
			beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
		}
        //先初始化 LoadTimeWeaverAware 类型的 Bean
		String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
		for (String weaverAwareName : weaverAwareNames) {
			getBean(weaverAwareName);
		}
       //停止使用用于类型匹配的临时类加载器
		beanFactory.setTempClassLoader(null);
      //冻结所有的bean定义，即已注册的bean定义将不会被修改或后处理
		beanFactory.freezeConfiguration();
      //初始化
		beanFactory.preInstantiateSingletons();
	}

上方没有解释的代码意义往下看吧

conversionService

这种类型的bean最实用的场景就是用来将前端传过来的参数和后端的controller方法上的参数格式转换的时候使用

例如：前端要传一个String，后端使用Date接受的时候就可以这样操作

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

public class StringToDateConverter implements Converter<String, Date> {

    @Override
    public Date convert(String date) {
        try {
            return dateFormat.parse(date);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("日期转换失败!");
            return null;
        }
        
    }
}

再搞个bean

1
2
3
4
5
6
7
 
<bean id="conversionService"
  class="org.springframework.context.support.ConversionServiceFactoryBean">
  <property name="converters">
    <list>
      <bean class="cn.shiyujun.utils.StringToDateConverter"/>
    </list>
  </property></bean>
EmbeddedValueResolver

利用EmbeddedValueResolver可以很方便的实现读取配置文件的属性

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
 
@Component
public class PropertiesUtil implements EmbeddedValueResolverAware {

    private StringValueResolver resolver;

    @Override
    public void setEmbeddedValueResolver(StringValueResolver resolver) {
        this.resolver = resolver;
    }

    /**
     * 获取属性时直接传入属性名称即可
     */
    public String getPropertiesValue(String key) {
        StringBuilder name = new StringBuilder("${").append(key).append("}");
        return resolver.resolveStringValue(name.toString());
    }

}
初始化

敲黑板了，重点来了。。。

这里分析beanFactory.preInstantiateSingletons()方法

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
65
66
 
public void preInstantiateSingletons() throws BeansException {
   if (this.logger.isDebugEnabled()) {
      this.logger.debug("Pre-instantiating singletons in " + this);
   }
   // this.beanDefinitionNames 保存了所有的 beanNames
   List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);

   for (String beanName : beanNames) {

      // 合并父 Bean 中的配置，主意<bean id="" class="" parent="" /> 中的 parent属性
      RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);

      // 不是抽象类、是单例的且不是懒加载的
      if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
         // 处理 FactoryBean
         if (isFactoryBean(beanName)) {
            //在 beanName 前面加上“&” 符号
            final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
            // 判断当前 FactoryBean 是否是 SmartFactoryBean 的实现
            boolean isEagerInit;
            if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
               isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                  @Override
                  public Boolean run() {
                     return ((SmartFactoryBean<?>) factory).isEagerInit();
                  }
               }, getAccessControlContext());
            }
            else {
               isEagerInit = (factory instanceof SmartFactoryBean &&
                     ((SmartFactoryBean<?>) factory).isEagerInit());
            }
            if (isEagerInit) {

               getBean(beanName);
            }
         }
         else {
            // 不是FactoryBean的直接使用此方法进行初始化
            getBean(beanName);
         }
      }
   }

  
   // 如果bean实现了 SmartInitializingSingleton 接口的，那么在这里得到回调
   for (String beanName : beanNames) {
      Object singletonInstance = getSingleton(beanName);
      if (singletonInstance instanceof SmartInitializingSingleton) {
         final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
         if (System.getSecurityManager() != null) {
            AccessController.doPrivileged(new PrivilegedAction<Object>() {
               @Override
               public Object run() {
                  smartSingleton.afterSingletonsInstantiated();
                  return null;
               }
            }, getAccessControlContext());
         }
         else {
            smartSingleton.afterSingletonsInstantiated();
         }
      }
   }
}

可以看到，不管是不是FactoryBean，最后都调用了getBean(beanName)，继续看这个方法吧

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
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
 
@Override
public Object getBean(String name) throws BeansException {
   return doGetBean(name, null, null, false);
}

protected <T> T doGetBean(
      final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
      throws BeansException {
   // 获取beanName，处理两种情况，一个是前面说的 FactoryBean(前面带 ‘&’)，再一个这个方法是可以根据别名来获取Bean的，所以在这里是要转换成最正统的BeanName
  //主要逻辑就是如果是FactoryBean就把&去掉如果是别名就把根据别名获取真实名称后面就不贴代码了
   final String beanName = transformedBeanName(name);

   //最后的返回值
   Object bean; 

   // 检查是否已初始化
   Object sharedInstance = getSingleton(beanName);
  //如果已经初始化过了，且没有传args参数就代表是get，直接取出返回
   if (sharedInstance != null && args == null) {
      if (logger.isDebugEnabled()) {
         if (isSingletonCurrentlyInCreation(beanName)) {
            logger.debug("...");
         }
         else {
            logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
         }
      }
      // 这里如果是普通Bean 的话，直接返回，如果是 FactoryBean 的话，返回它创建的那个实例对象
      bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
   }

   else {
	   // 如果存在prototype类型的这个bean
      if (isPrototypeCurrentlyInCreation(beanName)) {
                throw new BeanCurrentlyInCreationException(beanName);
      }

      // 如果当前BeanDefinition不存在这个bean且具有父BeanFactory
      BeanFactory parentBeanFactory = getParentBeanFactory();
      if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
         String nameToLookup = originalBeanName(name);
		// 返回父容器的查询结果
         if (args != null) {
            return (T) parentBeanFactory.getBean(nameToLookup, args);
         }
         else {
            return parentBeanFactory.getBean(nameToLookup, requiredType);
         }
      }

      if (!typeCheckOnly) {
         // typeCheckOnly 为 false，将当前 beanName 放入一个 alreadyCreated 的 Set 集合中。
         markBeanAsCreated(beanName);
      }

      /*
       * 到这就要创建bean了
       */
      try {
         final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
         checkMergedBeanDefinition(mbd, beanName, args);

         // 先初始化依赖的所有 Bean， depends-on 中定义的依赖
         String[] dependsOn = mbd.getDependsOn();
         if (dependsOn != null) {
            for (String dep : dependsOn) {
               // 检查是不是有循环依赖
               if (isDependent(beanName, dep)) {
                  throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                        "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
               }
               // 注册一下依赖关系
               registerDependentBean(dep, beanName);
               // 先初始化被依赖项
               getBean(dep);
            }
         }

         // 如果是单例的
         if (mbd.isSingleton()) {
            sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
               @Override
               public Object getObject() throws BeansException {
                  try {
                     // 执行创建 Bean，下面说
                     return createBean(beanName, mbd, args);
                  }
                  catch (BeansException ex) {
                     destroySingleton(beanName);
                     throw ex;
                  }
               }
            });
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
         }

         // 如果是prototype
         else if (mbd.isPrototype()) {
            Object prototypeInstance = null;
            try {
               beforePrototypeCreation(beanName);
               // 执行创建 Bean
               prototypeInstance = createBean(beanName, mbd, args);
            }
            finally {
               afterPrototypeCreation(beanName);
            }
            bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
         }

         // 如果不是 singleton 和 prototype 那么就是自定义的scope、例如Web项目中的session等类型，这里就交给自定义scope的应用方去实现
         else {
            String scopeName = mbd.getScope();
            final Scope scope = this.scopes.get(scopeName);
            if (scope == null) {
               throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
            }
            try {
               Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                  @Override
                  public Object getObject() throws BeansException {
                     beforePrototypeCreation(beanName);
                     try {
                        // 执行创建 Bean
                        return createBean(beanName, mbd, args);
                     }
                     finally {
                        afterPrototypeCreation(beanName);
                     }
                  }
               });
               bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
            }
            catch (IllegalStateException ex) {
               throw new BeanCreationException(beanName,
                     "Scope '" + scopeName + "' is not active for the current thread; consider " +
                     "defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                     ex);
            }
         }
      }
      catch (BeansException ex) {
         cleanupAfterBeanCreationFailure(beanName);
         throw ex;
      }
   }

   //检查bean的类型
   if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
      try {
         return getTypeConverter().convertIfNecessary(bean, requiredType);
      }
      catch (TypeMismatchException ex) {
         if (logger.isDebugEnabled()) {
            logger.debug("Failed to convert bean '" + name + "' to required type '" +
                  ClassUtils.getQualifiedName(requiredType) + "'", ex);
         }
         throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
      }
   }
   return (T) bean;
}

看了上方方法我们知道了原来Spring本身只定义了两种Scope，也知道了SpringMVC的几种Scope是如何实现的了。

然后发现一开始会先判断bean存不存在，如果存在就直接返回了。如果不存在那就要接着往下看createBean方法了

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
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
 
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
   if (logger.isDebugEnabled()) {
      logger.debug("Creating instance of bean '" + beanName + "'");
   }
   RootBeanDefinition mbdToUse = mbd;

   // 确保 BeanDefinition 中的 Class 被加载
   Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
   if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
      mbdToUse = new RootBeanDefinition(mbd);
      mbdToUse.setBeanClass(resolvedClass);
   }

   // 准备方法覆写，如果bean中定义了 <lookup-method /> 和 <replaced-method />
   try {
      mbdToUse.prepareMethodOverrides();
   }
   catch (BeanDefinitionValidationException ex) {
      throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
            beanName, "Validation of method overrides failed", ex);
   }

   try {
      // 如果有代理的话直接返回
      Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
      if (bean != null) {
         return bean; 
      }
   }
   catch (Throwable ex) {
      throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
            "BeanPostProcessor before instantiation of bean failed", ex);
   }
   // 创建 bean
   Object beanInstance = doCreateBean(beanName, mbdToUse, args);
   if (logger.isDebugEnabled()) {
      logger.debug("Finished creating instance of bean '" + beanName + "'");
   }
   return beanInstance;
}

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
      throws BeanCreationException {

   BeanWrapper instanceWrapper = null;
   if (mbd.isSingleton()) {
	 //如果是.factoryBean则从缓存删除
      instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
   }
   if (instanceWrapper == null) {
      // 实例化 Bean，这个方法里面才是终点，下面说
      instanceWrapper = createBeanInstance(beanName, mbd, args);
   }
	//bean实例
   final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
	//bean类型
   Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
   mbd.resolvedTargetType = beanType;

   synchronized (mbd.postProcessingLock) {
      if (!mbd.postProcessed) {
         try {
            // 循环调用实现了MergedBeanDefinitionPostProcessor接口的postProcessMergedBeanDefinition方法
		   // Spring对这个接口有几个默认的实现，其中大家最熟悉的一个是操作@Autowired注解的
            applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
         }
         catch (Throwable ex) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                  "Post-processing of merged bean definition failed", ex);
         }
         mbd.postProcessed = true;
      }
   }

 
   // 解决循环依赖问题
   boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
         isSingletonCurrentlyInCreation(beanName));
   if (earlySingletonExposure) {
      if (logger.isDebugEnabled()) {
         logger.debug("Eagerly caching bean '" + beanName +
               "' to allow for resolving potential circular references");
      }
	 //当正在创建A时，A依赖B，此时通过（8将A作为ObjectFactory放入单例工厂中进行early expose，此处B需要引用A，但A正在创建，从单例工厂拿到ObjectFactory，从而允许循环依赖
      addSingletonFactory(beanName, new ObjectFactory<Object>() {
         @Override
         public Object getObject() throws BeansException {
            return getEarlyBeanReference(beanName, mbd, bean);
         }
      });
   }

   Object exposedObject = bean;
   try {
      // 负责属性装配,很重要，下面说
      populateBean(beanName, mbd, instanceWrapper);
      if (exposedObject != null) {
         // 这里是处理bean初始化完成后的各种回调，例如init-method、InitializingBean 接口、BeanPostProcessor 接口
         exposedObject = initializeBean(beanName, exposedObject, mbd);
      }
   }
   catch (Throwable ex) {
      if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
         throw (BeanCreationException) ex;
      }
      else {
         throw new BeanCreationException(
               mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
      }
   }
	//同样的，如果存在循环依赖
   if (earlySingletonExposure) {
      Object earlySingletonReference = getSingleton(beanName, false);
      if (earlySingletonReference != null) {
         if (exposedObject == bean) {
            exposedObject = earlySingletonReference;
         }
         else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
            String[] dependentBeans = getDependentBeans(beanName);
            Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
            for (String dependentBean : dependentBeans) {
               if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                  actualDependentBeans.add(dependentBean);
               }
            }
            if (!actualDependentBeans.isEmpty()) {
               throw new BeanCurrentlyInCreationException(beanName,
                     "Bean with name '" + beanName + "' has been injected into other beans [" +
                     StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
                     "] in its raw version as part of a circular reference, but has eventually been " +
                     "wrapped. This means that said other beans do not use the final version of the " +
                     "bean. This is often the result of over-eager type matching - consider using " +
                     "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
            }
         }
      }
   }

   // 把bean注册到相应的Scope中
   try {
      registerDisposableBeanIfNecessary(beanName, bean, mbd);
   }
   catch (BeanDefinitionValidationException ex) {
      throw new BeanCreationException(
            mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
   }

   return exposedObject;
}

到这里第一次初始化的bean也返回了，你以为就这样结束了么。不，还有几个很重要的点

创建bean实例createBeanInstance ()
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
 
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
   // 确保已经加载了此 class
   Class<?> beanClass = resolveBeanClass(mbd, beanName);

   // 校验类的访问权限
   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());
   }
   
   if (mbd.getFactoryMethodName() != null)  {
      // 采用工厂方法实例化
      return instantiateUsingFactoryMethod(beanName, mbd, args);
   }

  //是否第一次
   boolean resolved = false;
  //是否采用构造函数注入
   boolean autowireNecessary = false;
   if (args == null) {
      synchronized (mbd.constructorArgumentLock) {
         if (mbd.resolvedConstructorOrFactoryMethod != null) {
            resolved = true;
            autowireNecessary = mbd.constructorArgumentsResolved;
         }
      }
   }
   if (resolved) {
      if (autowireNecessary) {
         return autowireConstructor(beanName, mbd, null, null);
      }
      else {
         // 无参构造函数
         return instantiateBean(beanName, mbd);
      }
   }

   // 判断是否采用有参构造函数
   Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
   if (ctors != null ||
         mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
         mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
      // 构造函数依赖注入
      return autowireConstructor(beanName, mbd, ctors, args);
   }

   // 调用无参构造函数
   return instantiateBean(beanName, mbd);
}

选一个无参的构造看一下吧

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
65
66
67
 
protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
   try {
      Object beanInstance;
      final BeanFactory parent = this;
      if (System.getSecurityManager() != null) {
         beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
            @Override
            public Object run() {

               return getInstantiationStrategy().instantiate(mbd, beanName, parent);
            }
         }, getAccessControlContext());
      }
      else {
         // 具体实例化的实现，往下看
         beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
      }
      BeanWrapper bw = new BeanWrapperImpl(beanInstance);
      initBeanWrapper(bw);
      return bw;
   }
   catch (Throwable ex) {
      throw new BeanCreationException(
            mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
   }
}

public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {

   // 如果不存在方法覆写，那就使用 java 反射进行实例化，否则使用 CGLIB,
   if (bd.getMethodOverrides().isEmpty()) {
      Constructor<?> constructorToUse;
      synchronized (bd.constructorArgumentLock) {
         constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
         if (constructorToUse == null) {
            final Class<?> clazz = bd.getBeanClass();
            if (clazz.isInterface()) {
               throw new BeanInstantiationException(clazz, "Specified class is an interface");
            }
            try {
               if (System.getSecurityManager() != null) {
                  constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() {
                     @Override
                     public Constructor<?> run() throws Exception {
                        return clazz.getDeclaredConstructor((Class[]) null);
                     }
                  });
               }
               else {
                  constructorToUse = clazz.getDeclaredConstructor((Class[]) null);
               }
               bd.resolvedConstructorOrFactoryMethod = constructorToUse;
            }
            catch (Throwable ex) {
               throw new BeanInstantiationException(clazz, "No default constructor found", ex);
            }
         }
      }
      // 利用构造方法进行实例化
      return BeanUtils.instantiateClass(constructorToUse);
   }
   else {
      // 存在方法覆写，利用 CGLIB 来完成实例化，需要依赖于 CGLIB 生成子类，这里就不展开了
      return instantiateWithMethodInjection(bd, beanName, owner);
   }
}
bean属性注入populateBean ()
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
65
66
67
68
69
70
71
72
73
74
75
 
protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
   // bean的所有属性
   PropertyValues pvs = mbd.getPropertyValues();

   if (bw == null) {
      if (!pvs.isEmpty()) {
         throw new BeanCreationException(
               mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
      }
      else {
         return;
      }
   }

   boolean continueWithPropertyPopulation = true;
   if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
      for (BeanPostProcessor bp : getBeanPostProcessors()) {
         if (bp instanceof InstantiationAwareBeanPostProcessor) {
            InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
            // 如果返回 false，代表不需要进行后续的属性设值，也不需要再经过其他的 BeanPostProcessor 的处理
            if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
               continueWithPropertyPopulation = false;
               break;
            }
         }
      }
   }

   if (!continueWithPropertyPopulation) {
      return;
   }

   if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
         mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
      MutablePropertyValues newPvs = new MutablePropertyValues(pvs);

      // 通过名字找到所有属性值，如果是 bean 依赖，先初始化依赖的 bean。记录依赖关系
      if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
         autowireByName(beanName, mbd, bw, newPvs);
      }

      // 通过类型装配。复杂一些
      if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
         autowireByType(beanName, mbd, bw, newPvs);
      }

      pvs = newPvs;
   }

   boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
   boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);

   if (hasInstAwareBpps || needsDepCheck) {
      PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
      if (hasInstAwareBpps) {
         for (BeanPostProcessor bp : getBeanPostProcessors()) {
            if (bp instanceof InstantiationAwareBeanPostProcessor) {
               InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
               // 这里就是上方曾经提到过得对@Autowired处理的一个BeanPostProcessor了
               // 它会对所有标记@Autowired、@Value 注解的属性进行设值
               pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
               if (pvs == null) {
                  return;
               }
            }
         }
      }
      if (needsDepCheck) {
         checkDependencies(beanName, mbd, filteredPds, pvs);
      }
   }
   // 设置 bean 实例的属性值
   applyPropertyValues(beanName, mbd, bw, pvs);
}

getBean这一块就搞完了

13. finishRefresh()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
 
protected void finishRefresh() {
		//看名字就知道了，清理刚才一系列操作使用到的资源缓存
		clearResourceCaches();

		// 初始化LifecycleProcessor
		initLifecycleProcessor();

		// 这个方法的内部实现是启动所有实现了Lifecycle接口的bean
		getLifecycleProcessor().onRefresh();

		//发布ContextRefreshedEvent事件
		publishEvent(new ContextRefreshedEvent(this));

		// 检查spring.liveBeansView.mbeanDomain是否存在，有就会创建一个MBeanServer
		LiveBeansView.registerApplicationContext(this);
	}
14. resetCommonCaches()

最后还是一步还是清除缓存

15. refresh()总结

上方用了这么长的篇幅把整个refresh()方法的细节给梳理清楚，这里再把刚开始看的懵懵的refresh()方法贴一下

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
 

public void refresh() throws BeansException, IllegalStateException {
 
   synchronized (this.startupShutdownMonitor) {

      // 记录容器的启动时间、标记“已启动”状态、检查环境变量
      prepareRefresh();

      // 初始化BeanFactory容器、注册BeanDefinition
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

      // 设置 BeanFactory 的类加载器，添加几个 BeanPostProcessor，手动注册几个特殊的 bean
      prepareBeanFactory(beanFactory);

      try {
         // 扩展点
         postProcessBeanFactory(beanFactory);
         // 调用 BeanFactoryPostProcessor 各个实现类的 postProcessBeanFactory(factory) 方法
         invokeBeanFactoryPostProcessors(beanFactory);

         // 注册 BeanPostProcessor 的实现类
         registerBeanPostProcessors(beanFactory);

         // 初始化MessageSource
         initMessageSource();

         // 初始化事件广播器
         initApplicationEventMulticaster();

         // 扩展点
         onRefresh();

         // 注册事件监听器
         registerListeners();

         // 初始化所有的 singleton beans
         finishBeanFactoryInitialization(beanFactory);

         // 广播事件
         finishRefresh();
      }

      catch (BeansException ex) {
         if (logger.isWarnEnabled()) {
            logger.warn("Exception encountered during context initialization - " +
                  "cancelling refresh attempt: " + ex);
         }

         // 销毁已经初始化的的Bean
         destroyBeans();

         // 设置 'active' 状态
         cancelRefresh(ex);

         throw ex;
      }

      finally {
         // 清除缓存
         resetCommonCaches();
      }
   }
}

总结

至此，本文到此结束。鉴于XML方式比较简单、通俗易懂，所以本文基于XML的方式大致介绍了SpringIOC的启动流程、稍微深入的讲解了Bean容器的创建以及Bean的初始化过程。这也是作者第一次阅读开源框架的源码，如文章有错误之处还请您费心指出。

鉴于现在比较流行SpringBoot和SpringCloud，下篇文章将会从基于注解的方向分析SpringIOC

SpringIOC源码解析（下）的更多相关文章

  1. springIOC源码解析之BeanDefinition的注册

    ApplicationContext类结构 context是一个存储上下文结构的东西,里面会引用BeanFactory  BeanFactory类结构 我们从这句代码开始分析,(本文spring采用的 ...

  2. SpringIOC源码解析（上）

    注意,看完这篇文章需要很长很长很长时间... 准备工作 本文会分析Spring的IOC模块的整体流程,分析过程需要使用一个简单的demo工程来启动Spring,demo工程我以备好,需要的童鞋自行在下 ...

  3. Laravel学习笔记之Session源码解析(下)

    说明:在中篇中学习了session的CRUD增删改查操作,本篇主要学习关闭session的相关源码.实际上,在Laravel5.3中关闭session主要包括两个过程:保存当前URL到session介 ...

  4. springIOC源码解析之Bean的创建

    上一篇讲到了beanFactory的配置文件的解析和beanFactory的创建,都集中到了obtainFreshBeanFactory();这一句代码里了,本篇主要讲bean的创建过程 public ...

  5. axios 源码解析(下) 拦截器的详解

    axios的除了初始化配置外,其它有用的应该就是拦截器了,拦截器分为请求拦截器和响应拦截器两种: 请求拦截器    ;在请求发送前进行一些操作,例如在每个请求体里加上token,统一做了处理如果以后要 ...

  6. Spring源码解析系列汇总

    相信我,你会收藏这篇文章的 本篇文章是这段时间撸出来的Spring源码解析系列文章的汇总,总共包含以下专题.喜欢的同学可以收藏起来以备不时之需 SpringIOC源码解析(上) 本篇文章搭建了IOC源 ...

  7. erlang下lists模块sort（排序）方法源码解析(二)

    上接erlang下lists模块sort(排序)方法源码解析(一),到目前为止,list列表已经被分割成N个列表,而且每个列表的元素是有序的(从大到小) 下面我们重点来看看mergel和rmergel ...

  8. erlang下lists模块sort（排序）方法源码解析(一)

    排序算法一直是各种语言最简单也是最复杂的算法,例如十大经典排序算法(动图演示)里面讲的那样 第一次看lists的sort方法的时候,蒙了,几百行的代码,我心想要这么复杂么(因为C语言的冒泡排序我记得不 ...

  9. 渣渣菜鸡的 ElasticSearch 源码解析 —— 启动流程（下）

    关注我 转载请务必注明原创地址为:http://www.54tianzhisheng.cn/2018/08/12/es-code03/ 前提 上篇文章写完了 ES 流程启动的一部分,main 方法都入 ...

随机推荐

  1. linux关闭ACPI电源管理模块

    一.运行环境 # cat /etc/redhat-release CentOS release 6.2 (Final) # uname -a Linux web-server- -.el6.x86_6 ...

  2. IDEA安装maven和设置自动配置下载包

    在我们开发的过程中如果环境配置好了,对于我们开发将优很大作用,减少可开发的时间,接下来我就讲解一下maven的安装和配置,以及在idea上配置,希望此教程同时对大家优帮助. 1.1.下载maven和安 ...

  3. python GIL全局解释器锁,多线程多进程效率比较,进程池,协程,TCP服务端实现协程

    GIL全局解释器锁 ''' python解释器: - Cpython C语言 - Jpython java ... 1.GIL: 全局解释器锁 - 翻译: 在同一个进程下开启的多线程,同一时刻只能有一 ...

  4. Node.js到底是做什么的？这是我看到最好的解释了

    作者:贾厂长链接:https://www.zhihu.com/question/33578075/answer/56951771来源:知乎著作权归作者所有.商业转载请联系作者获得授权,非商业转载请注明 ...

  5. 【Spring IoC】IoC介绍（一）

    IoC(Inversion of Control)的职责:原先由程序员主动通过new实例化对象这个事情,现在交由Spring负责,即由IoC容器负责. Spring 容器是 Spring 框架的核心. ...

  6. （转）Tomcat与Jetty区别

    一.简介 Tomcat: Tomcat是Apache软件基金会(Apache Software Foundation)的Jakarta项目中的一个核心项目,由Apache.Sun和其他一些公司及个人共 ...

  7. HTTP几种认证方式介绍

    HTTP提供了一套标准的身份验证框架:服务器可以用来针对客户端的请求发送质询(challenge),客户端根据质询提供身份验证凭证.质询与应答的工作流程如下:服务器端向客户端返回401(Unautho ...

  8. [LeetCode] 659. Split Array into Consecutive Subsequences 将数组分割成连续子序列

    You are given an integer array sorted in ascending order (may contain duplicates), you need to split ...

  9. SpringBootThymeleaf案例

    一.添加依赖 <!-- 添加thymeleaf模版的依赖 --> <dependency> <groupId>org.springframework.boot< ...

  10. Java 性能调优小技巧

    1.在知道必要之前不要优化系统 这可能是最重要的性能调整技巧之一.你应该遵循常见的最佳实践做法并尝试高效地实现用例.但是,这并不意味着在你证明必要之前,你应该更换任何标准库或构建复杂的优化. 在大多数 ...