Spring4源码解析：BeanDefinition架构及实现

一、架构图

首先共同看下总体的 Java Class Diagrams 图：

二、具体类实现

2.1 AttributeAccessor

接口定义了一个通用的可对任意对象获取、修改等操作元数据的附加契约。主要方法如下：

public interface AttributeAccessor {
    void setAttribute(String name, Object value);
    Object getAttribute(String name);
    Object removeAttribute(String name);
    boolean hasAttribute(String name);
    String[] attributeNames();
}

2.2 AttributeAccessorSupport

抽象类，AttributeAccessor支持类，主要针对属性CRUD操作。

主要方法、属性如下：

public abstract class AttributeAccessorSupport implements AttributeAccessor, Serializable {
    private final Map<String, Object> attributes = new LinkedHashMap<String, Object>(0);

    @Override
    public void setAttribute(String name, Object value)

    @Override
    public Object getAttribute(String name)

    @Override
    public Object removeAttribute(String name)

    @Override
    public boolean hasAttribute(String name)

    @Override
    public String[] attributeNames()

    protected void copyAttributesFrom(AttributeAccessor source)

    @Override
    public boolean equals(Object other) 

    @Override
    public int hashCode()
}

2.3 BeanMetadataElement

用于传输配置源对象（对象的确切类型将取决于所使用的配置机制），在配置源对象中可获取 bean 元数据元素。主要方法：

public interface BeanMetadataElement {
    Object getSource();
}

2.4 BeanMetadataAttributeAccessor

为了追踪对象定义源，实现了BeanMetadataElement接口的getResource()方法也提供了 AttributeAccessorSupport 针对属性的增删改查。主要方法如下：

private Object source;

public void setSource(Object source) 

@Override
public Object getSource()  

public void addMetadataAttribute(BeanMetadataAttribute attribute)  

//bean definition定义中属性键值对容器
public BeanMetadataAttribute getMetadataAttribute(String name)  

@Override
public void setAttribute(String name, Object value)  

@Override
public Object getAttribute(String name)  

@Override
public Object removeAttribute(String name)

2.5 BeanDefinition

配置文件元素标签在容器中内部表示形式，一个BeanDefinition描述了一个bean的实例，包括属性值，构造方法参数值和继承自它的类的更多信息。

BeanDefinition仅仅是一个最简单的接口，主要功能是允许BeanFactoryPostProcessor，比如实现类 PropertyPlaceHolderConfigure 能够检索并修改属性值和别的bean的元数据。

主要方法：

public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
    //单例作用域
    String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;

    //原型作用域
    String SCOPE_PROTOTYPE = ConfigurableBeanFactory.SCOPE_PROTOTYPE;

    //Bean角色，
    int ROLE_APPLICATION = 0;  //应用程序重要组成部分
    int ROLE_SUPPORT = 1;  //做为大量配置的一部分（支持、扩展类）
    int ROLE_INFRASTRUCTURE = 2;  //指内部工作的基础构造

    String getParentName();
    void setParentName(String parentName);

    String getBeanClassName();
    void setBeanClassName(String beanClassName);

    String getFactoryBeanName();
    void setFactoryBeanName(String factoryBeanName);

    String getFactoryMethodName();
    void setFactoryMethodName(String factoryMethodName);

    String getScope();
    void setScope(String scope);

    boolean isLazyInit();
    void setLazyInit(boolean lazyInit);

    //获取依赖 bean name（详见depends-on属性用法）
    String[] getDependsOn();
    void setDependsOn(String... dependsOn);

    //自动装配
    boolean isAutowireCandidate();
    void setAutowireCandidate(boolean autowireCandidate);

    boolean isPrimary();
    void setPrimary(boolean primary);

    ConstructorArgumentValues getConstructorArgumentValues();
    MutablePropertyValues getPropertyValues();

    boolean isSingleton();
    boolean isPrototype();

    boolean isAbstract();

    int getRole();

    String getDescription();

    String getResourceDescription();

    BeanDefinition getOriginatingBeanDefinition();
}

2.6 AbstractBeanDefinition

配置文件元素标签在容器中内部表示形式，一个BeanDefinition描述了一个bean的实例，包括属性值，构造方法参数值和继承自它的类的更多信息。

BeanDefinition仅仅是一个最简单的接口，主要功能是允许BeanFactoryPostProcessor，比如实现类 PropertyPlaceHolderConfigure 能够检索并修改属性值和别的bean的元数据。

主要方法：

@SuppressWarnings("serial")
public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccessor
		implements BeanDefinition, Cloneable {

    //默认作用域singleton，单例
    public static final String SCOPE_DEFAULT = "";

    //不自动装配
    public static final int AUTOWIRE_NO = AutowireCapableBeanFactory.AUTOWIRE_NO;

    //按名称装配
    public static final int AUTOWIRE_BY_NAME = AutowireCapableBeanFactory.AUTOWIRE_BY_NAME;

    //按类型装配
    public static final int AUTOWIRE_BY_TYPE = AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE;

    //构造器装配
    public static final int AUTOWIRE_CONSTRUCTOR = AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR;

    //已过时，不赞成使用
    @Deprecated
    public static final int AUTOWIRE_AUTODETECT = AutowireCapableBeanFactory.AUTOWIRE_AUTODETECT;

    //依赖检查：无依赖
    public static final int DEPENDENCY_CHECK_NONE = 0;

    //依赖检查：对象间引用
    public static final int DEPENDENCY_CHECK_OBJECTS = 1;

    //依赖检查：会核对所有的原始类型和String类型的属性
    public static final int DEPENDENCY_CHECK_SIMPLE = 2;

    //依赖检查：所有属性
    public static final int DEPENDENCY_CHECK_ALL = 3;

    //bean标签中 destroyMethod=""
    public static final String INFER_METHOD = "(inferred)";

    private volatile Object beanClass;

    private String scope = SCOPE_DEFAULT;

    private boolean abstractFlag = false;

    private boolean lazyInit = false;

    private int autowireMode = AUTOWIRE_NO;

    private int dependencyCheck = DEPENDENCY_CHECK_NONE;

	private String[] dependsOn;

    private boolean autowireCandidate = true;

    private boolean primary = false;

    private final Map<String, AutowireCandidateQualifier> qualifiers =
			new LinkedHashMap<String, AutowireCandidateQualifier>(0);

    private boolean nonPublicAccessAllowed = true;

    private boolean lenientConstructorResolution = true;

    private ConstructorArgumentValues constructorArgumentValues;

    private MutablePropertyValues propertyValues;

    private MethodOverrides methodOverrides = new MethodOverrides();

    private String factoryBeanName;

    private String factoryMethodName;

    private String initMethodName;

    private String destroyMethodName;

    private boolean enforceInitMethod = true;

    private boolean enforceDestroyMethod = true;

    private boolean synthetic = false;

    private int role = BeanDefinition.ROLE_APPLICATION;

    private String description;

    private Resource resource;

    protected AbstractBeanDefinition() {
		this(null, null);
	}

    protected AbstractBeanDefinition(ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        setConstructorArgumentValues(cargs);
        setPropertyValues(pvs);
    }

    //深复制一个原有的beandefinition
    protected AbstractBeanDefinition(BeanDefinition original) {
        setParentName(original.getParentName());
        setBeanClassName(original.getBeanClassName());
        setFactoryBeanName(original.getFactoryBeanName());
        setFactoryMethodName(original.getFactoryMethodName());
        setScope(original.getScope());
        setAbstract(original.isAbstract());
        setLazyInit(original.isLazyInit());
        setRole(original.getRole());
        setConstructorArgumentValues(new ConstructorArgumentValues(original.getConstructorArgumentValues()));
        setPropertyValues(new MutablePropertyValues(original.getPropertyValues()));
        setSource(original.getSource());
        copyAttributesFrom(original);

        if (original instanceof AbstractBeanDefinition) {
            AbstractBeanDefinition originalAbd = (AbstractBeanDefinition) original;
            if (originalAbd.hasBeanClass()) {
                setBeanClass(originalAbd.getBeanClass());
            }
            setAutowireMode(originalAbd.getAutowireMode());
            setDependencyCheck(originalAbd.getDependencyCheck());
            setDependsOn(originalAbd.getDependsOn());
            setAutowireCandidate(originalAbd.isAutowireCandidate());
            copyQualifiersFrom(originalAbd);
            setPrimary(originalAbd.isPrimary());
            setNonPublicAccessAllowed(originalAbd.isNonPublicAccessAllowed());
            setLenientConstructorResolution(originalAbd.isLenientConstructorResolution());
            setInitMethodName(originalAbd.getInitMethodName());
            setEnforceInitMethod(originalAbd.isEnforceInitMethod());
            setDestroyMethodName(originalAbd.getDestroyMethodName());
            setEnforceDestroyMethod(originalAbd.isEnforceDestroyMethod());
            setMethodOverrides(new MethodOverrides(originalAbd.getMethodOverrides()));
            setSynthetic(originalAbd.isSynthetic());
            setResource(originalAbd.getResource());
        }else {
            setResourceDescription(original.getResourceDescription());
        }
    }

    //覆盖当前BeanDefinition
    public void overrideFrom(BeanDefinition other) {
        if (StringUtils.hasLength(other.getBeanClassName())) {
            setBeanClassName(other.getBeanClassName());
        }
        if (StringUtils.hasLength(other.getFactoryBeanName())) {
            setFactoryBeanName(other.getFactoryBeanName());
        }
        if (StringUtils.hasLength(other.getFactoryMethodName())) {
            setFactoryMethodName(other.getFactoryMethodName());
        }
        if (StringUtils.hasLength(other.getScope())) {
            setScope(other.getScope());
        }
        setAbstract(other.isAbstract());
        setLazyInit(other.isLazyInit());
        setRole(other.getRole());
        getConstructorArgumentValues().addArgumentValues(other.getConstructorArgumentValues());
        getPropertyValues().addPropertyValues(other.getPropertyValues());
        setSource(other.getSource());
        copyAttributesFrom(other);

        if (other instanceof AbstractBeanDefinition) {
            AbstractBeanDefinition otherAbd = (AbstractBeanDefinition) other;
            if (otherAbd.hasBeanClass()) {
                setBeanClass(otherAbd.getBeanClass());
            }
            setAutowireCandidate(otherAbd.isAutowireCandidate());
            setAutowireMode(otherAbd.getAutowireMode());
            copyQualifiersFrom(otherAbd);
            setPrimary(otherAbd.isPrimary());
            setDependencyCheck(otherAbd.getDependencyCheck());
            setDependsOn(otherAbd.getDependsOn());
            setNonPublicAccessAllowed(otherAbd.isNonPublicAccessAllowed());
            setLenientConstructorResolution(otherAbd.isLenientConstructorResolution());
            if (StringUtils.hasLength(otherAbd.getInitMethodName())) {
                setInitMethodName(otherAbd.getInitMethodName());
                setEnforceInitMethod(otherAbd.isEnforceInitMethod());
            }
            if (StringUtils.hasLength(otherAbd.getDestroyMethodName())) {
                setDestroyMethodName(otherAbd.getDestroyMethodName());
                setEnforceDestroyMethod(otherAbd.isEnforceDestroyMethod());
            }
            getMethodOverrides().addOverrides(otherAbd.getMethodOverrides());
            setSynthetic(otherAbd.isSynthetic());
            setResource(otherAbd.getResource());
        }
        else {
            setResourceDescription(other.getResourceDescription());
        }
    }

    //将提供的默认值应用于此bean。
    public void applyDefaults(BeanDefinitionDefaults defaults) {
        setLazyInit(defaults.isLazyInit());
        setAutowireMode(defaults.getAutowireMode());
        setDependencyCheck(defaults.getDependencyCheck());
        setInitMethodName(defaults.getInitMethodName());
        setEnforceInitMethod(false);
        setDestroyMethodName(defaults.getDestroyMethodName());
        setEnforceDestroyMethod(false);
    }

    public boolean hasBeanClass() {
        return (this.beanClass instanceof Class);
    }

    public void setBeanClass(Class<?> beanClass) {
        this.beanClass = beanClass;
    }

    //若已经解析就返回这个包装类。
    public Class<?> getBeanClass() throws IllegalStateException {
        Object beanClassObject = this.beanClass;
        if (beanClassObject == null) {
            throw new IllegalStateException("No bean class specified on bean definition");
        }
        if (!(beanClassObject instanceof Class)) {
            throw new IllegalStateException(
                    "Bean class name [" + beanClassObject + "] has not been resolved into an actual Class");
        }
        return (Class<?>) beanClassObject;
    }

    @Override
    public void setBeanClassName(String beanClassName) {
        this.beanClass = beanClassName;
    }

    @Override
    public String getBeanClassName() {
        Object beanClassObject = this.beanClass;
        if (beanClassObject instanceof Class) {
            return ((Class<?>) beanClassObject).getName();
        }
        else {
            return (String) beanClassObject;
        }
    }

    //解析类
    public Class<?> resolveBeanClass(ClassLoader classLoader) throws ClassNotFoundException {
        String className = getBeanClassName();
        if (className == null) {
            return null;
        }
        Class<?> resolvedClass = ClassUtils.forName(className, classLoader);
        this.beanClass = resolvedClass;
        return resolvedClass;
    }

    @Override
    public void setScope(String scope) {
        this.scope = scope;
    }

    @Override
    public String getScope() {
        return this.scope;
    }

    @Override
    public boolean isSingleton() {
        return SCOPE_SINGLETON.equals(scope) || SCOPE_DEFAULT.equals(scope);
    }

    @Override
    public boolean isPrototype() {
        return SCOPE_PROTOTYPE.equals(scope);
    }

    public void setAbstract(boolean abstractFlag) {
        this.abstractFlag = abstractFlag;
    }

    @Override
    public boolean isAbstract() {
        return this.abstractFlag;
    }

    @Override
    public void setLazyInit(boolean lazyInit) {
        this.lazyInit = lazyInit;
    }

    @Override
    public boolean isLazyInit() {
        return this.lazyInit;
    }

    public void setAutowireMode(int autowireMode) {
        this.autowireMode = autowireMode;
    }

    public int getAutowireMode() {
        return this.autowireMode;
    }

    public int getResolvedAutowireMode() {
        if (this.autowireMode == AUTOWIRE_AUTODETECT) {
            // Work out whether to apply setter autowiring or constructor autowiring.
            // If it has a no-arg constructor it's deemed to be setter autowiring,
            // otherwise we'll try constructor autowiring.
            Constructor<?>[] constructors = getBeanClass().getConstructors();
            for (Constructor<?> constructor : constructors) {
                if (constructor.getParameterTypes().length == 0) {
                    return AUTOWIRE_BY_TYPE;
                }
            }
            return AUTOWIRE_CONSTRUCTOR;
        }
        else {
            return this.autowireMode;
        }
    }

    public void setDependencyCheck(int dependencyCheck) {
        this.dependencyCheck = dependencyCheck;
    }

    public int getDependencyCheck() {
        return this.dependencyCheck;
    }

    @Override
    public void setDependsOn(String... dependsOn) {
        this.dependsOn = dependsOn;
    }

    @Override
    public String[] getDependsOn() {
        return this.dependsOn;
    }

    @Override
    public void setAutowireCandidate(boolean autowireCandidate) {
        this.autowireCandidate = autowireCandidate;
    }

    @Override
    public boolean isAutowireCandidate() {
        return this.autowireCandidate;
    }

    @Override
    public void setPrimary(boolean primary) {
        this.primary = primary;
    }

    @Override
    public boolean isPrimary() {
        return this.primary;
    }

    public void addQualifier(AutowireCandidateQualifier qualifier) {
        this.qualifiers.put(qualifier.getTypeName(), qualifier);
    }

    public boolean hasQualifier(String typeName) {
        return this.qualifiers.keySet().contains(typeName);
    }

    public AutowireCandidateQualifier getQualifier(String typeName) {
        return this.qualifiers.get(typeName);
    }

    public Set<AutowireCandidateQualifier> getQualifiers() {
        return new LinkedHashSet<AutowireCandidateQualifier>(this.qualifiers.values());
    }

    public void copyQualifiersFrom(AbstractBeanDefinition source) {
        Assert.notNull(source, "Source must not be null");
        this.qualifiers.putAll(source.qualifiers);
    }

    //指定是否允许访问非公共构造函数和方法
    public void setNonPublicAccessAllowed(boolean nonPublicAccessAllowed) {
        this.nonPublicAccessAllowed = nonPublicAccessAllowed;
    }

    public boolean isNonPublicAccessAllowed() {
        return this.nonPublicAccessAllowed;
    }

    //构造器宽松模式或非宽松模式。
    public void setLenientConstructorResolution(boolean lenientConstructorResolution)
    public boolean isLenientConstructorResolution()

    //构造函数参数
    public void setConstructorArgumentValues(ConstructorArgumentValues constructorArgumentValues)
    @Override
    public ConstructorArgumentValues getConstructorArgumentValues()
    public boolean hasConstructorArgumentValues()

    public void setPropertyValues(MutablePropertyValues propertyValues)
    @Override
    public MutablePropertyValues getPropertyValues()

    public void setMethodOverrides(MethodOverrides methodOverrides)
    public MethodOverrides getMethodOverrides()

    @Override
    public void setFactoryBeanName(String factoryBeanName)
    @Override
    public String getFactoryBeanName()

    @Override
    public void setFactoryMethodName(String factoryMethodName)
    @Override
    public String getFactoryMethodName()

    public void setInitMethodName(String initMethodName)
    public String getInitMethodName()

    //InitMethod默认配置, 默认值false
    public void setEnforceInitMethod(boolean enforceInitMethod)
     public boolean isEnforceInitMethod()

    public void setDestroyMethodName(String destroyMethodName)
    public String getDestroyMethodName()

    //DestroyMethod默认配置, 默认值false
    public void setEnforceDestroyMethod(boolean enforceDestroyMethod)
    public boolean isEnforceDestroyMethod() 

    //一个合成的beandefinition
    public void setSynthetic(boolean synthetic)
    public boolean isSynthetic()

    public void setRole(int role)
    @Override
    public int getRole()

    public void setDescription(String description)
    @Override
    public String getDescription()

    public void setResource(Resource resource)
    public Resource getResource()

    public void setResourceDescription(String resourceDescription)
    @Override
    public String getResourceDescription()

    public void setOriginatingBeanDefinition(BeanDefinition originatingBd)
    @Override
    public BeanDefinition getOriginatingBeanDefinition()

    public void validate() throws BeanDefinitionValidationException 

    //校验这个bean定义的需要覆盖的方面
    public void prepareMethodOverrides() throws BeanDefinitionValidationException

    //验证覆盖的方法
    protected void prepareMethodOverride(MethodOverride mo) throws BeanDefinitionValidationException 

    //覆写Object的clone() */
    @Override
    public Object clone()

    public abstract AbstractBeanDefinition cloneBeanDefinition();

    @Override
    public boolean equals(Object other)  

    @Override
    public int hashCode() 

    @Override
    public String toString()
}

2.7 AnnotatedBeanDefinition

public interface AnnotatedBeanDefinition extends BeanDefinition {
    //获取该bean definition的注解元数据。
    AnnotationMetadata getMetadata();

    //获取该bean definition的注解元数据。
    MethodMetadata getFactoryMethodMetadata();
}

2.8 RootBeanDefinition

RootBeanDefinition用来在配置阶段进行注册bean definition。

表明它是一个可合并的bean definition,即在spring beanFactory运行期间，可以返回一个特定的bean。RootBeanDefinition作为一个重要的通用的bean definition 视图。但在spring 4后，有的更好的选择：GenericBeanDefinition。

public class RootBeanDefinition extends AbstractBeanDefinition {

    boolean allowCaching = true;

    private BeanDefinitionHolder decoratedDefinition;

    private volatile Class<?> targetType;

    boolean isFactoryMethodUnique = false;

    final Object constructorArgumentLock = new Object();

    Object resolvedConstructorOrFactoryMethod;

    volatile Class<?> resolvedFactoryMethodReturnType;

    boolean constructorArgumentsResolved = false;

    Object[] resolvedConstructorArguments;

    Object[] preparedConstructorArguments;

    final Object postProcessingLock = new Object();

    boolean postProcessed = false;

    volatile Boolean beforeInstantiationResolved;

    private Set<Member> externallyManagedConfigMembers;

    private Set<String> externallyManagedInitMethods;

    private Set<String> externallyManagedDestroyMethods;

    public RootBeanDefinition() {
        super();
    }

    //创建一个单例的RootBeanDefinition
    public RootBeanDefinition(Class<?> beanClass) {
        super();
        setBeanClass(beanClass);
    }

    public RootBeanDefinition(Class<?> beanClass, int autowireMode, boolean dependencyCheck) {
        super();
        setBeanClass(beanClass);
        setAutowireMode(autowireMode);
        if (dependencyCheck && getResolvedAutowireMode() != AUTOWIRE_CONSTRUCTOR) {
            setDependencyCheck(RootBeanDefinition.DEPENDENCY_CHECK_OBJECTS);
        }
    }

    public RootBeanDefinition(Class<?> beanClass, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        super(cargs, pvs);
        setBeanClass(beanClass);
    }

    public RootBeanDefinition(String beanClassName) {
        setBeanClassName(beanClassName);
    }

    public RootBeanDefinition(String beanClassName, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        super(cargs, pvs);
        setBeanClassName(beanClassName);
    }

    //创建RootBeanDefinition，深度复制参数中的bean definition
    public RootBeanDefinition(RootBeanDefinition original) {
        super(original);
        this.allowCaching = original.allowCaching;
        this.decoratedDefinition = original.decoratedDefinition;
        this.targetType = original.targetType;
        this.isFactoryMethodUnique = original.isFactoryMethodUnique;
    }

    RootBeanDefinition(BeanDefinition original) {
        super(original);
    }

    @Override
    public String getParentName() {
        return null;
    }

    @Override
    public void setParentName(String parentName) {
        if (parentName != null) {
            throw new IllegalArgumentException("Root bean cannot be changed into a child bean with parent reference");
        }
    }

    public void setDecoratedDefinition(BeanDefinitionHolder decoratedDefinition) {
        this.decoratedDefinition = decoratedDefinition;
    }

    public BeanDefinitionHolder getDecoratedDefinition() {
        return this.decoratedDefinition;
    }

    public void setTargetType(Class<?> targetType) {
        this.targetType = targetType;
    }

    public Class<?> getTargetType() {
        return this.targetType;
    }

    //指定一个工厂方法的名称,唯一、无重载的
    public void setUniqueFactoryMethodName(String name) {
        Assert.hasText(name, "Factory method name must not be empty");
        setFactoryMethodName(name);
        this.isFactoryMethodUnique = true;
    }

    //检查参数方法是能成为factory method
    public boolean isFactoryMethod(Method candidate) {
        return (candidate != null && candidate.getName().equals(getFactoryMethodName()));
    }

    //返回解析后的工厂方法作为Java对象方法,如果可用。
    public Method getResolvedFactoryMethod() {
        synchronized (this.constructorArgumentLock) {
            Object candidate = this.resolvedConstructorOrFactoryMethod;
            return (candidate instanceof Method ? (Method) candidate : null);
        }
    }

    public void registerExternallyManagedConfigMember(Member configMember) {
        synchronized (this.postProcessingLock) {
            if (this.externallyManagedConfigMembers == null) {
                this.externallyManagedConfigMembers = new HashSet<Member>(1);
            }
            this.externallyManagedConfigMembers.add(configMember);
        }
    }

    public boolean isExternallyManagedConfigMember(Member configMember) {
        synchronized (this.postProcessingLock) {
            return (this.externallyManagedConfigMembers != null &&
                    this.externallyManagedConfigMembers.contains(configMember));
        }
    }

    public void registerExternallyManagedInitMethod(String initMethod) {
        synchronized (this.postProcessingLock) {
            if (this.externallyManagedInitMethods == null) {
                this.externallyManagedInitMethods = new HashSet<String>(1);
            }
            this.externallyManagedInitMethods.add(initMethod);
        }
    }

    public boolean isExternallyManagedInitMethod(String initMethod) {
        synchronized (this.postProcessingLock) {
            return (this.externallyManagedInitMethods != null &&
                    this.externallyManagedInitMethods.contains(initMethod));
        }
    }

    public void registerExternallyManagedDestroyMethod(String destroyMethod) {
        synchronized (this.postProcessingLock) {
            if (this.externallyManagedDestroyMethods == null) {
                this.externallyManagedDestroyMethods = new HashSet<String>(1);
            }
            this.externallyManagedDestroyMethods.add(destroyMethod);
        }
    }

    public boolean isExternallyManagedDestroyMethod(String destroyMethod) {
        synchronized (this.postProcessingLock) {
            return (this.externallyManagedDestroyMethods != null &&
                    this.externallyManagedDestroyMethods.contains(destroyMethod));
        }
    }

    @Override
    public RootBeanDefinition cloneBeanDefinition() {
        return new RootBeanDefinition(this);
    }

    @Override
    public boolean equals(Object other) {
        return (this == other || (other instanceof RootBeanDefinition && super.equals(other)));
    }

    @Override
    public String toString() {
        return "Root bean: " + super.toString();
    }
}

2.9 ConfigurationClassBeanDefinition

是ConfigurationClassBeanDefinitionReader的内部类，ConfigurationClassBeanDefinitionReader读取一组完全填充了属性的配置实例，通过context内给定的BeanDefinitionRegistry进行注册bean definition。

private static class ConfigurationClassBeanDefinition extends RootBeanDefinition implements AnnotatedBeanDefinition {

    private final AnnotationMetadata annotationMetadata;

    private final MethodMetadata factoryMethodMetadata;

    public ConfigurationClassBeanDefinition(ConfigurationClass configClass, MethodMetadata beanMethodMetadata) {
        this.annotationMetadata = configClass.getMetadata();
        this.factoryMethodMetadata = beanMethodMetadata;
        setLenientConstructorResolution(false);
    }

    public ConfigurationClassBeanDefinition(
            RootBeanDefinition original, ConfigurationClass configClass, MethodMetadata beanMethodMetadata) {
        super(original);
        this.annotationMetadata = configClass.getMetadata();
        this.factoryMethodMetadata = beanMethodMetadata;
    }

    private ConfigurationClassBeanDefinition(ConfigurationClassBeanDefinition original) {
        super(original);
        this.annotationMetadata = original.annotationMetadata;
        this.factoryMethodMetadata = original.factoryMethodMetadata;
    }

    @Override
    public AnnotationMetadata getMetadata() {
        return this.annotationMetadata;
    }

    @Override
    public MethodMetadata getFactoryMethodMetadata() {
        return this.factoryMethodMetadata;
    }

    @Override
    public boolean isFactoryMethod(Method candidate) {
        return (super.isFactoryMethod(candidate) && BeanAnnotationHelper.isBeanAnnotated(candidate));
    }

    @Override
    public ConfigurationClassBeanDefinition cloneBeanDefinition() {
        return new ConfigurationClassBeanDefinition(this);
    }
}

2.10 ChildBeanDefinition

public class ChildBeanDefinition extends AbstractBeanDefinition {

    private String parentName;

    //指定父类名称，创建子类。
    public ChildBeanDefinition(String parentName) {
        super();
        this.parentName = parentName;
    }

    public ChildBeanDefinition(String parentName, MutablePropertyValues pvs) {
        super(null, pvs);
        this.parentName = parentName;
    }

    public ChildBeanDefinition(String parentName, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        super(cargs, pvs);
        this.parentName = parentName;
    }

    public ChildBeanDefinition(String parentName, Class<?> beanClass, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        super(cargs, pvs);
        this.parentName = parentName;
        setBeanClass(beanClass);
    }

    public ChildBeanDefinition(String parentName, String beanClassName, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
        super(cargs, pvs);
        this.parentName = parentName;
        setBeanClassName(beanClassName);
    }

    public ChildBeanDefinition(ChildBeanDefinition original) {
        super(original);
    }

    @Override
    public void setParentName(String parentName) {
        this.parentName = parentName;
    }

    @Override
    public String getParentName() {
        return this.parentName;
    }

    @Override
    public void validate() throws BeanDefinitionValidationException {
        super.validate();
        if (this.parentName == null) {
            throw new BeanDefinitionValidationException("'parentName' must be set in ChildBeanDefinition");
        }
    }

    @Override
    public AbstractBeanDefinition cloneBeanDefinition() {
        return new ChildBeanDefinition(this);
    }

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof ChildBeanDefinition)) {
            return false;
        }
        ChildBeanDefinition that = (ChildBeanDefinition) other;
        return (ObjectUtils.nullSafeEquals(this.parentName, that.parentName) && super.equals(other));
    }

    @Override
    public int hashCode() {
        return ObjectUtils.nullSafeHashCode(this.parentName) * 29 + super.hashCode();
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("Child bean with parent '");
        sb.append(this.parentName).append("': ").append(super.toString());
        return sb.toString();
    }
}

2.11 GenericBeanDefinition

GenericBeanDefinition是通用的标准bean definition，除了具有指定类可选的构造参数值、属性参数或其它bean definition一样的特性外，还具有parenetName属性，这也意味着可以用来灵活设置parent bean definition。

GenericBeanDefinition的使用会越来越广，而ChildBeanDefinition很可能会被替代。

public class GenericBeanDefinition extends AbstractBeanDefinition {

    private String parentName;

    public GenericBeanDefinition() {
        super();
    }

    //深度复制
    public GenericBeanDefinition(BeanDefinition original) {
        super(original);
    }

    @Override
    public void setParentName(String parentName) {
        this.parentName = parentName;
    }

    @Override
    public String getParentName() {
        return this.parentName;
    }

    @Override
    public AbstractBeanDefinition cloneBeanDefinition() {
        return new GenericBeanDefinition(this);
    }

    @Override
    public boolean equals(Object other) {
        return (this == other || (other instanceof GenericBeanDefinition && super.equals(other)));
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("Generic bean");
        if (this.parentName != null) {
            sb.append(" with parent '").append(this.parentName).append("'");
        }
        sb.append(": ").append(super.toString());
        return sb.toString();
    }
}

2.12 ScannedGenericBeanDefinition

基于asm的类解析器，是GenericBeanDefinition类的扩展，支持注解元数据，这种支持通过AnnotatedBeanDefinition接口实现。

@SuppressWarnings("serial")
public class ScannedGenericBeanDefinition extends GenericBeanDefinition implements AnnotatedBeanDefinition {

    private final AnnotationMetadata metadata;

    public ScannedGenericBeanDefinition(MetadataReader metadataReader) {
        Assert.notNull(metadataReader, "MetadataReader must not be null");
        this.metadata = metadataReader.getAnnotationMetadata();
        setBeanClassName(this.metadata.getClassName());
    }

    @Override
    public final AnnotationMetadata getMetadata() {
        return this.metadata;
    }

    @Override
    public MethodMetadata getFactoryMethodMetadata() {
        return null;
    }
}

2.13 AnnotatedGenericBeanDefinition

对应注解@Bean。

@SuppressWarnings("serial")
public class AnnotatedGenericBeanDefinition extends GenericBeanDefinition implements AnnotatedBeanDefinition {

    private final AnnotationMetadata metadata;

    private MethodMetadata factoryMethodMetadata;

    public AnnotatedGenericBeanDefinition(Class<?> beanClass) {
        setBeanClass(beanClass);
        this.metadata = new StandardAnnotationMetadata(beanClass, true);
    }

    public AnnotatedGenericBeanDefinition(AnnotationMetadata metadata) {
        Assert.notNull(metadata, "AnnotationMetadata must not be null");
        if (metadata instanceof StandardAnnotationMetadata) {
            setBeanClass(((StandardAnnotationMetadata) metadata).getIntrospectedClass());
        } else {
            setBeanClassName(metadata.getClassName());
        }
        this.metadata = metadata;
    }

    public AnnotatedGenericBeanDefinition(AnnotationMetadata metadata, MethodMetadata factoryMethodMetadata) {
        this(metadata);
        Assert.notNull(factoryMethodMetadata, "MethodMetadata must not be null");
        setFactoryMethodName(factoryMethodMetadata.getMethodName());
        this.factoryMethodMetadata = factoryMethodMetadata;
    }

    @Override
    public final AnnotationMetadata getMetadata() {
         return this.metadata;
    }

    @Override
    public final MethodMetadata getFactoryMethodMetadata() {
        return this.factoryMethodMetadata;
  }
}