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SpringMVC 源代码深度解析<context:component-scan>（扫描和注册的注解Bean）

2017-07-28 19:14 826 查看

我们在SpringMVC开发项目中，有的用注解和XML配置Bean,这两种都各有自己的优势，数据源配置比较经常用XML配置，控制层依赖的service比较经常用注解等（在部署时比较不会改变的），我们经常比较常用的注解有@Component是通用标注，@Controller标注web控制器，@Service标注Servicec层的服务，@Respository标注DAO层的数据访问。SpringMVC启动时怎么被自动扫描然后解析并注册到Bean工厂中去（放到DefaultListableBeanFactory中的Map<String, BeanDefinition> beanDefinitionMap中以BeanName为key）？我们今天带着这些问题来了解分析这实现的过程，我们在分析之前先了解一下这些注解。

@Controller标注web控制器，@Service标注Service层的服务，@Respository标注DAO层的数据访问。@Component是通用标注，只是定义为一个类为Bean，SpringMVC会把所有添加@Component注解的类作为使用自动扫描注入配置路径下的备选对象。@Controller、@Service\@Respository只是更加的细化，都是被@Component标注，所以我们比较不推荐使用@Component。源代码如下：



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@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Service {
    String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
    String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {
    String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Service {
String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
String value() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {
String value() default "";
}

都是有标示@Component

我们在配置文件中，标示配置需要扫描哪些包下，也可以配置对某个包下不扫描，代码如下：

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<context:component-scan base-package="cn.test">
        <context:exclude-filter type="regex" expression="cn.test.*.*.controller"/>
        <context:exclude-filter type="regex" expression="cn.test.*.*.controller2"/>
</context:component-scan>

<context:component-scan base-package="cn.test">
<context:exclude-filter type="regex" expression="cn.test.*.*.controller"/>
<context:exclude-filter type="regex" expression="cn.test.*.*.controller2"/>
</context:component-scan>

说明：

   <context:exclude-filter>指定的不扫描包，<context:exclude-filter>指定的扫描包

SpringMVC先读取配置文件，然后根据context:component-scan中属性base-package去扫描指定包下的class和jar文件，把标示@Controller标注web控制器，@Service标注Servicec层的服务，@Respository标注DAO层的数据访问等注解的都获取，并注册为Bean类放到Bean工厂，我们接下来要分析的这个过程。我们平时项目开发都是这样的注解，实现MVC模式，代码如下：

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例如：
//控制层
@Controller
@RequestMapping(value="/test")
public class TestController2 {
    @Autowired
    private TestService testService;
    @RequestMapping(value="/index")
    public String getIndex(Model model){

        return "";
    }
}

//服务层
@Service("testService")
public class TestServiceImpl implements  TestService{
}

例如：
//控制层
@Controller
@RequestMapping(value="/test")
public class TestController2 {
@Autowired
private TestService testService;
@RequestMapping(value="/index")
public String getIndex(Model model){

return "";
}
}

//服务层
@Service("testService")
public class TestServiceImpl implements  TestService{
}

我们今天的入口点就在这，因为解析注解的到注册，也是先读取配置文件并解析，在解析时扫描对应包下的Java类，里面有DefaultBeanDefinitionDocumentReader这个类，doRegisterBeanDefinitions这个方法实现解析配置文件的Bean，这边已经读取进来形成Document 形式存储，然后开始解析Bean,是由BeanDefinitionParserDelegate类实现的，BeanDefinitionParserDelegate完成具体Bean的解析（例如：bean标签、import标签等）这个在上一篇SpringMVC
源代码深度解析 IOC容器（Bean 解析、注册）里有解析，今天注解属于扩展的标签，是由NamespaceHandler和BeanDefinitionParser来解析。源代码如下：

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public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
        String namespaceUri = getNamespaceURI(ele);
        NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
        if (handler == null) {
            error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
            return null;
        }
        return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
    }

public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
String namespaceUri = getNamespaceURI(ele);
NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
if (handler == null) {
error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele);
return null;
}
return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}

NamespaceHandler这边这边起到了什么作用，根据不同的Namespace获取不同的NamespaceHandler，因为我们在Beans标签配置了命名空间，然后就可以配置对应的标签，解析标签时，比较有自己的所实现的NamespaceHandler来解析，如图所示：

   NamespaceHandler中的parse方法是它的子类类NamespaceHa
18978
ndlerSupport实现的，获取通过findParserForElement方法获取BeanDefinitionParser 对象，这个对象在工程初始化时就直接实例化放在缓存中Map<String, BeanDefinitionParser>，然后通过localName获取，源代码如下：

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public BeanDefinition parse(Element element, ParserContext parserContext) {
    return findParserForElement(element, parserContext).parse(element, parserContext);
}
private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) {
    String localName = parserContext.getDelegate().getLocalName(element);
    BeanDefinitionParser parser = this.parsers.get(localName);
    if (parser == null) {
        parserContext.getReaderContext().fatal(
                "Cannot locate BeanDefinitionParser for element [" + localName + "]", element);
    }
    return parser;
}

public BeanDefinition parse(Element element, ParserContext parserContext) {
return findParserForElement(element, parserContext).parse(element, parserContext);
}
private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) {
String localName = parserContext.getDelegate().getLocalName(element);
BeanDefinitionParser parser = this.parsers.get(localName);
if (parser == null) {
parserContext.getReaderContext().fatal(
"Cannot locate BeanDefinitionParser for element [" + localName + "]", element);
}
return parser;
}

为什么要获取BeanDefinitionParser ，因为BeanDefinitionParser 类是解析配置文件中的<context:component-scan>,<aop:config>等标签，但是不同的标签是由不同的BeanDefinitionParser来进行解析的，如图所示：

接下来我们开始解析这个标签， <context:component-scan>标签的解析是由ComponentScanBeanDefinitionParser类解析的，接下来我们要分析它怎么解析注解的Bean，并把Bean注册到Bean工厂，源代码如下：



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public BeanDefinition parse(Element element, ParserContext parserContext) {
       //获取context:component-scan 配置的属性base-package的值
    String[] basePackages = StringUtils.tokenizeToStringArray(element.getAttribute(BASE_PACKAGE_ATTRIBUTE),
            ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
       //创建扫描对应包下的class文件的对象
    ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
       //扫描对应包下的class文件并有注解的Bean包装成BeanDefinition
    Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
    registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
    return null;
}

public BeanDefinition parse(Element element, ParserContext parserContext) {
//获取context:component-scan 配置的属性base-package的值
String[] basePackages = StringUtils.tokenizeToStringArray(element.getAttribute(BASE_PACKAGE_ATTRIBUTE),
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
//创建扫描对应包下的class文件的对象
ClassPathBeanDefinitionScanner scanner = configureScanner(parserContext, element);
//扫描对应包下的class文件并有注解的Bean包装成BeanDefinition
Set<BeanDefinitionHolder> beanDefinitions = scanner.doScan(basePackages);
registerComponents(parserContext.getReaderContext(), beanDefinitions, element);
return null;
}

说明：

（1）获取context:component-scan 配置的属性base-package的值，然后放到数组。

    （2）创建扫描对应包下的class和jar文件的对象ClassPathBeanDefinitionScanner ，由这个类来实现扫描包下的class和jar文件并把注解的Bean包装成BeanDefinition。

    （3）BeanDefinition注册到Bean工厂。

第一：扫描是由ComponentScanBeanDefinitionParser的doScan方法来实现的，源代码如下：

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protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
       //新建队列来保存BeanDefinitionHolder
    Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>();
       //循环需要扫描的包
    for (String basePackage : basePackages) {
           //进行扫描注解并包装成BeanDefinition
        Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
        for (BeanDefinition candidate : candidates) {
            ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
            candidate.setScope(scopeMetadata.getScopeName());
            String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
            if (candidate instanceof AbstractBeanDefinition) {
                postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
            }
            if (candidate instanceof AnnotatedBeanDefinition) {
                AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
            }
            if (checkCandidate(beanName, candidate)) {
                BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
                beanDefinitions.add(definitionHolder);
                   //对BeanDefinition进行注册
                registerBeanDefinition(definitionHolder, this.registry);
            }
        }
    }
    return beanDefinitions;
}

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
//新建队列来保存BeanDefinitionHolder
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>();
//循环需要扫描的包
for (String basePackage : basePackages) {
//进行扫描注解并包装成BeanDefinition
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//对BeanDefinition进行注册
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}

进行扫描注解并包装成BeanDefinition是ComponentScanBeanDefinitionParser由父类ClassPathScanningCandidateComponentProvider的方法findCandidateComponents实现的，源代码如下：



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public Set<BeanDefinition> findCandidateComponents(String basePackage) {
    Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();
    try {
          //base-package中的值替换为classpath*:cn/test/**/*.class
        String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
                resolveBasePackage(basePackage) + "/" + this.resourcePattern;
           //获取所以base-package下的资源
        Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
           boolean traceEnabled = logger.isTraceEnabled();
        boolean debugEnabled = logger.isDebugEnabled();
        for (Resource resource : resources) {
            if (traceEnabled) {
                logger.trace("Scanning " + resource);
            }
            if (resource.isReadable()) {
                try {
                    MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
                        //对context:exclude-filter进行过滤
                    if (isCandidateComponent(metadataReader)) {
                          //包装BeanDefinition
                        ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
                        sbd.setResource(resource);
                        sbd.setSource(resource);
                        if (isCandidateComponent(sbd)) {
                            if (debugEnabled) {
                                logger.debug("Identified candidate component class: " + resource);
                            }
                            candidates.add(sbd);
                        }
                        else {
                            if (debugEnabled) {
                                logger.debug("Ignored because not a concrete top-level class: " + resource);
                            }
                        }
                    }
                    else {
                        if (traceEnabled) {
                            logger.trace("Ignored because not matching any filter: " + resource);
                        }
                    }
                }
                catch (Throwable ex) {
                    throw new BeanDefinitionStoreException(
                            "Failed to read candidate component class: " + resource, ex);
                }
            }
            else {
                if (traceEnabled) {
                    logger.trace("Ignored because not readable: " + resource);
                }
            }
        }
    }
    catch (IOException ex) {
        throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
    }
      return candidates;
}

public Set<BeanDefinition> findCandidateComponents(String basePackage) {
Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();
try {
//base-package中的值替换为classpath*:cn/test/**/*.class
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
resolveBasePackage(basePackage) + "/" + this.resourcePattern;
//获取所以base-package下的资源
Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
boolean traceEnabled = logger.isTraceEnabled();
boolean debugEnabled = logger.isDebugEnabled();
for (Resource resource : resources) {
if (traceEnabled) {
logger.trace("Scanning " + resource);
}
if (resource.isReadable()) {
try {
MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
//对context:exclude-filter进行过滤
if (isCandidateComponent(metadataReader)) {
//包装BeanDefinition
ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader);
sbd.setResource(resource);
sbd.setSource(resource);
if (isCandidateComponent(sbd)) {
if (debugEnabled) {
logger.debug("Identified candidate component class: " + resource);
}
candidates.add(sbd);
}
else {
if (debugEnabled) {
logger.debug("Ignored because not a concrete top-level class: " + resource);
}
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not matching any filter: " + resource);
}
}
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to read candidate component class: " + resource, ex);
}
}
else {
if (traceEnabled) {
logger.trace("Ignored because not readable: " + resource);
}
}
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex);
}
return candidates;
}

说明：

     (1)先根据context:component-scan 中属性的base-package="cn.test"配置转换为classpath*:cn/test/**/*.class，并扫描对应下的class和jar文件并获取类对应的路径，返回Resources

     (2)根据<context:exclude-filter>指定的不扫描包，<context:exclude-filter>指定的扫描包配置进行过滤不包含的包对应下的class和jar。

    （3）封装成BeanDefinition放到队列里。

1）怎么根据packageSearchPath获取包对应下的class路径，是通过PathMatchingResourcePatternResolver类，findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));获取配置包下的class路径并封装成Resource，实现也是getClassLoader().getResources(path);实现的。源代码如下：

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<span style="font-size:18px;">public Resource[] getResources(String locationPattern) throws IOException {
        Assert.notNull(locationPattern, "Location pattern must not be null");
        if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
            // a class path resource (multiple resources for same name possible)
            if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
                // a class path resource pattern
                return findPathMatchingResources(locationPattern);
            }
            else {
                // all class path resources with the given name
                return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
            }
        }
        else {
            // Only look for a pattern after a prefix here
            // (to not get fooled by a pattern symbol in a strange prefix).
            int prefixEnd = locationPattern.indexOf(":") + 1;
            if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
                // a file pattern
                return findPathMatchingResources(locationPattern);
            }
            else {
                // a single resource with the given name
                return new Resource[] {getResourceLoader().getResource(locationPattern)};
            }
        }
    }

protected Resource[] findAllClassPathResources(String location) throws IOException {
        String path = location;
        if (path.startsWith("/")) {
            path = path.substring(1);
        }
        Enumeration<URL> resourceUrls = getClassLoader().getResources(path);
        Set<Resource> result = new LinkedHashSet<Resource>(16);
        while (resourceUrls.hasMoreElements()) {
            URL url = resourceUrls.nextElement();
            result.add(convertClassLoaderURL(url));
        }
        return result.toArray(new Resource[result.size()]);
    }
</span>

<span style="font-size:18px;">public Resource[] getResources(String locationPattern) throws IOException {
Assert.notNull(locationPattern, "Location pattern must not be null");
if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {
// a class path resource (multiple resources for same name possible)
if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {
// a class path resource pattern
return findPathMatchingResources(locationPattern);
}
else {
// all class path resources with the given name
return findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));
}
}
else {
// Only look for a pattern after a prefix here
// (to not get fooled by a pattern symbol in a strange prefix).
int prefixEnd = locationPattern.indexOf(":") + 1;
if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {
// a file pattern
return findPathMatchingResources(locationPattern);
}
else {
// a single resource with the given name
return new Resource[] {getResourceLoader().getResource(locationPattern)};
}
}
}

protected Resource[] findAllClassPathResources(String location) throws IOException {
String path = location;
if (path.startsWith("/")) {
path = path.substring(1);
}
Enumeration<URL> resourceUrls = getClassLoader().getResources(path);
Set<Resource> result = new LinkedHashSet<Resource>(16);
while (resourceUrls.hasMoreElements()) {
URL url = resourceUrls.nextElement();
result.add(convertClassLoaderURL(url));
}
return result.toArray(new Resource[result.size()]);
}
</span>

说明：getClassLoader().getResources获取classpath*:cn/test/**/*.class下的cn/test包下的class的路径信息。并返回了URL。这里能把对应class路径获取到了，就能获取里面的信息。

2）isCandidateComponent实现的标签是里配置的<context:exclude-filter>指定的不扫描包，<context:exclude-filter>指定的扫描包的过滤，源代码如下：



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<span style="font-size:18px;">protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
        for (TypeFilter tf : this.excludeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return false;
            }
        }
        for (TypeFilter tf : this.includeFilters) {
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                AnnotationMetadata metadata = metadataReader.getAnnotationMetadata();
                if (!metadata.isAnnotated(Profile.class.getName())) {
                    return true;
                }
                AnnotationAttributes profile = MetadataUtils.attributesFor(metadata, Profile.class);
                return this.environment.acceptsProfiles(profile.getStringArray("value"));
            }
        }
        return false;
    }</span>

<span style="font-size:18px;">protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
for (TypeFilter tf : this.excludeFilters) {
if (tf.match(metadataReader, this.metadataReaderFactory)) {
return false;
}
}
for (TypeFilter tf : this.includeFilters) {
if (tf.match(metadataReader, this.metadataReaderFactory)) {
AnnotationMetadata metadata = metadataReader.getAnnotationMetadata();
if (!metadata.isAnnotated(Profile.class.getName())) {
return true;
}
AnnotationAttributes profile = MetadataUtils.attributesFor(metadata, Profile.class);
return this.environment.acceptsProfiles(profile.getStringArray("value"));
}
}
return false;
}</span>

说明： this.excludeFilters有pattern属性，值是就是<context:exclude-filter type="regex" expression="cn.test.*.*.controller"/>的cn.test.*.*.controller值this.pattern.matcher(metadata.getClassName()).matches();通过这个去匹配，如果是就返回false。如图所示：

我们到这边已经把对应的通过在XML配置把注解扫描解析并封装成BeanDefinition。
接下来我们来分析一下注册到Bean工厂，大家还记得ComponentScanBeanDefinitionParser的doScan方法，然后到工厂的是由registerBeanDefinition(definitionHolder, this.registry);实现的，源代码如下：

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protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
    BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
}

public static void registerBeanDefinition(
        BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
        throws BeanDefinitionStoreException {

    // Register bean definition under primary name.
    String beanName = definitionHolder.getBeanName();
    registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

    // Register aliases for bean name, if any.
    String[] aliases = definitionHolder.getAliases();
    if (aliases != null) {
        for (String aliase : aliases) {
            registry.registerAlias(beanName, aliase);
        }
    }
}

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
        throws BeanDefinitionStoreException {

    Assert.hasText(beanName, "Bean name must not be empty");
    Assert.notNull(beanDefinition, "BeanDefinition must not be null");

    if (beanDefinition instanceof AbstractBeanDefinition) {
        try {
            ((AbstractBeanDefinition) beanDefinition).validate();
        }
        catch (BeanDefinitionValidationException ex) {
            throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
                    "Validation of bean definition failed", ex);
        }
    }

    synchronized (this.beanDefinitionMap) {
        Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
        if (oldBeanDefinition != null) {
            if (!this.allowBeanDefinitionOverriding) {
                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
                        "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
                        "': There is already [" + oldBeanDefinition + "] bound.");
            }
            else {
                if (this.logger.isInfoEnabled()) {
                    this.logger.info("Overriding bean definition for bean '" + beanName +
                            "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
                }
            }
        }
        else {
            this.beanDefinitionNames.add(beanName);
            this.frozenBeanDefinitionNames = null;
        }
        this.beanDefinitionMap.put(beanName, beanDefinition);
    }

    resetBeanDefinition(beanName);
}

protected void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) {
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, registry);
}

public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {

// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

// Register aliases for bean name, if any.
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String aliase : aliases) {
registry.registerAlias(beanName, aliase);
}
}
}

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {

Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");

if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}

synchronized (this.beanDefinitionMap) {
Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
if (!this.allowBeanDefinitionOverriding) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
}
else {
this.beanDefinitionNames.add(beanName);
this.frozenBeanDefinitionNames = null;
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}

resetBeanDefinition(beanName);
}

说明：DefaultListableBeanFactory要实现的保存到Map<String, BeanDefinition> beanDefinitionMap中以BeanName为key，如果有，就不用保存了。DefaultListableBeanFactory我们在上一篇SpringMVC
源代码深度解析 IOC容器（Bean 解析、注册）有介绍过了，DefaultListableBeanFactory继承了BeanFactory。

总结：

（1）因为解析注解的到注册，也是先读取配置文件并解析，在解析时扫描对应包下的JAVA类，里面有DefaultBeanDefinitionDocumentReader这个类，doRegisterBeanDefinitions这个方法实现解析配置文件的Bean，这边已经读取进来形成Document 形式存储。然后注解属于扩展的标签，是由NamespaceHandler和BeanDefinitionParser来解析。

（2）根据context:component-scan中属性base-package去扫描指定包下的class和jar文件，获取对应的路径信息，然后根据配置<context:exclude-filter>指定的扫描包配置进行过滤不包含的包对应下的class和jar路径的Resources。

（3）把标示@Controller标注web控制器，@Service标注Servicec层的服务，@Respository标注DAO层的数据访问等注解路径都获取包装成BeanDefinition，并注册为Bean类放到Bean工厂，也就是DefaultListableBeanFactoryMap<String, BeanDefinition> beanDefinitionMap中以BeanName为key。

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