BeanDefinition是Spring中非常核心的概念，表示Bean定义，Spring根据BeanDefinition来创建Bean对象，
BeanDefinition有很多的属性用来描述Bean。
其类定义如下：
public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
String SCOPE_SINGLETON = ConfigurableBeanFactory.SCOPE_SINGLETON;
String SCOPE_PROTOTYPE = ConfigurableBeanFactory.SCOPE_PROTOTYPE;
int ROLE_APPLICATION = 0;
int ROLE_SUPPORT = 1;
int ROLE_INFRASTRUCTURE = 2;
// Modifiable attributes
void setParentName(String parentName);
String getParentName();
void setBeanClassName(String beanClassName);
String getBeanClassName();
void setScope(String scope);
String getScope();
void setLazyInit(boolean lazyInit);
boolean isLazyInit();
void setDependsOn(String... dependsOn);
String[] getDependsOn();
void setAutowireCandidate(boolean autowireCandidate);
boolean isAutowireCandidate();
void setPrimary(boolean primary);
boolean isPrimary();
void setFactoryBeanName(String factoryBeanName);
String getFactoryBeanName();
void setFactoryMethodName(String factoryMethodName);
String getFactoryMethodName();
ConstructorArgumentValues getConstructorArgumentValues();
MutablePropertyValues getPropertyValues();
// Read-only attributes
boolean isSingleton();
boolean isPrototype();
boolean isAbstract();
int getRole();
String getDescription();
String getResourceDescription();
BeanDefinition getOriginatingBeanDefinition();
}
定义了很多描述一个BeanDefinition的属性的setter和getter方法
- parentName：父BeanDefinition名，一般没有，只有父子关系的BeanDefinition才有
- beanClassName：表示一个bean的类型，比如UserService.class、OrderService.class，Spring在创建Bean的过程中会根据此属性来实例化得到对象。
- scope：表示一个bean的作用域，比如：scope等于singleton，该bean就是一个单例Bean; scope等于prototype，该bean就是一个原型Bean。
- lazyInit：表示一个bean是不是需要懒加载，prototype类型的bean的lazyInit属性不起作用。懒加载的单例bean，会在第一次getBean的时候生成该bean，非懒加载的单例bean，则会在Spring启动过程中直接生成好。
- dependsOn：表示一个bean在创建之前所依赖的其他bean，在一个bean创建之前，它所依赖的这些bean得先全部创建好。
- autowireCandidate：表示该bean是否支持自动注入候选
- primary：表示一个bean是主bean，在Spring中一个类型可以有多个bean对象，在进行依赖注入时，如果根据类型找到了多个bean并且没有使用@Qulifier指定，此时会判断这些bean中是否存在一个主bean，如果存在，则直接将这个bean注入给属性。
- factoryBeanName：工厂Bean名字，标注@Configuration的类
- factoryMethodName：工厂Bean方法名字，以上两者来自@Bean注解的
- constructorArgumentValues（ConstructorArgumentValues）：构造方法参数值
- propertyValues（MutablePropertyValues）：所有的属性值
- initMethodName：表示一个bean的初始化方法，一个bean的生命周期过程中有一个步骤叫初始化，Spring会在这个步骤中去调用bean的初始化方法，初始化逻辑由程序员自己控制，表示程序员可以自定义逻辑对bean进行加工。
其类继承层次如下：
BeanDefinition继承自AttributeAccessor，定义了属性获取和设置的方法，其基本实现AttributeAccessorSupport采用map。进一步的BeanMetadataAttributeAccessor采用BeanMetadataAttribute来包装了value。
public interface AttributeAccessor {
void setAttribute(String name, Object value);
Object getAttribute(String name);
Object removeAttribute(String name);
boolean hasAttribute(String name);
String[] attributeNames();
}
三、AbstractBeanDefinition
AbstractBeanDefinition是BeanDefinition的基础实现，定义了一系列的属性，并提供了getter/setter方法。具体的BeanDefinition实现（RootBeanDefinition、ChildBeanDefinition、GenericBeanDefinition）都继承自该类。
public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccessor
implements BeanDefinition, Cloneable {
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 qualifiers =
new LinkedHashMap(0);
private boolean nonPublicAccessAllowed = true;
private boolean lenientConstructorResolution = true;
private String factoryBeanName;
private String factoryMethodName;
private ConstructorArgumentValues constructorArgumentValues;
private MutablePropertyValues propertyValues;
private MethodOverrides methodOverrides = new MethodOverrides();
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;
。。。
四、RootBeanDefinition、ChildBeanDefinition、GenericBeanDefinition
RootBeanDefinition代表普通的BeanDefinition实现，通过其构造方法直接new BeanDefinition。ChildBeanDefinition 代表可以设置父BeanDefinition的。
GenericBeanDefinition代表一般的BeanDefinition，主要的两种实现AnnotatedGenericBeanDefinition和ScannedGenericBeanDefinition都继承自他。
AnnotatedBeanDefinition表示注解的BeanDefinition，有两种主要的实现AnnotatedGenericBeanDefinition和ScannedGenericBeanDefinition
public interface AnnotatedBeanDefinition extends BeanDefinition {
AnnotationMetadata getMetadata();
MethodMetadata getFactoryMethodMetadata();
}
六、AnnotatedGenericBeanDefinition
AnnotatedGenericBeanDefinition继承自GenericBeanDefinition，扩展了注解类的元信息和工厂方法元信息
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;
}
}
七、ScannedGenericBeanDefinition
该类代表扫描的BeanDefinition
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;
}
}
八、BeanDefinitionBuilder
BeanDefinitionBuilder通过建造者模式提供了方便生成和设置属性的BeanDefinition的方法。我们常常用它来生成RootBeanDefinition、ChildBeanDefinition、GenericBeanDefinition。
public class BeanDefinitionBuilder {
public static BeanDefinitionBuilder genericBeanDefinition() {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new GenericBeanDefinition();
return builder;
}
public static BeanDefinitionBuilder genericBeanDefinition(Class beanClass) {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new GenericBeanDefinition();
builder.beanDefinition.setBeanClass(beanClass);
return builder;
}
public static BeanDefinitionBuilder genericBeanDefinition(String beanClassName) {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new GenericBeanDefinition();
builder.beanDefinition.setBeanClassName(beanClassName);
return builder;
}
public static BeanDefinitionBuilder rootBeanDefinition(Class beanClass) {
return rootBeanDefinition(beanClass, null);
}
public static BeanDefinitionBuilder rootBeanDefinition(Class beanClass, String factoryMethodName) {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new RootBeanDefinition();
builder.beanDefinition.setBeanClass(beanClass);
builder.beanDefinition.setFactoryMethodName(factoryMethodName);
return builder;
}
public static BeanDefinitionBuilder rootBeanDefinition(String beanClassName) {
return rootBeanDefinition(beanClassName, null);
}
public static BeanDefinitionBuilder rootBeanDefinition(String beanClassName, String factoryMethodName) {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new RootBeanDefinition();
builder.beanDefinition.setBeanClassName(beanClassName);
builder.beanDefinition.setFactoryMethodName(factoryMethodName);
return builder;
}
public static BeanDefinitionBuilder childBeanDefinition(String parentName) {
BeanDefinitionBuilder builder = new BeanDefinitionBuilder();
builder.beanDefinition = new ChildBeanDefinition(parentName);
return builder;
}
private AbstractBeanDefinition beanDefinition;
private int constructorArgIndex;
private BeanDefinitionBuilder() {
}
public AbstractBeanDefinition getRawBeanDefinition() {
return this.beanDefinition;
}
public AbstractBeanDefinition getBeanDefinition() {
this.beanDefinition.validate();
return this.beanDefinition;
}
public BeanDefinitionBuilder setParentName(String parentName) {
this.beanDefinition.setParentName(parentName);
return this;
}
public BeanDefinitionBuilder setFactoryMethod(String factoryMethod) {
this.beanDefinition.setFactoryMethodName(factoryMethod);
return this;
}
public BeanDefinitionBuilder setFactoryMethodOnBean(String factoryMethod, String factoryBean) {
this.beanDefinition.setFactoryMethodName(factoryMethod);
this.beanDefinition.setFactoryBeanName(factoryBean);
return this;
}
@Deprecated
public BeanDefinitionBuilder addConstructorArg(Object value) {
return addConstructorArgValue(value);
}
public BeanDefinitionBuilder addConstructorArgValue(Object value) {
this.beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(
this.constructorArgIndex++, value);
return this;
}
public BeanDefinitionBuilder addConstructorArgReference(String beanName) {
this.beanDefinition.getConstructorArgumentValues().addIndexedArgumentValue(
this.constructorArgIndex++, new RuntimeBeanReference(beanName));
return this;
}
public BeanDefinitionBuilder addPropertyValue(String name, Object value) {
this.beanDefinition.getPropertyValues().add(name, value);
return this;
}
public BeanDefinitionBuilder addPropertyReference(String name, String beanName) {
this.beanDefinition.getPropertyValues().add(name, new RuntimeBeanReference(beanName));
return this;
}
public BeanDefinitionBuilder setInitMethodName(String methodName) {
this.beanDefinition.setInitMethodName(methodName);
return this;
}
public BeanDefinitionBuilder setDestroyMethodName(String methodName) {
this.beanDefinition.setDestroyMethodName(methodName);
return this;
}
public BeanDefinitionBuilder setScope(String scope) {
this.beanDefinition.setScope(scope);
return this;
}
public BeanDefinitionBuilder setAbstract(boolean flag) {
this.beanDefinition.setAbstract(flag);
return this;
}
public BeanDefinitionBuilder setLazyInit(boolean lazy) {
this.beanDefinition.setLazyInit(lazy);
return this;
}
public BeanDefinitionBuilder setAutowireMode(int autowireMode) {
beanDefinition.setAutowireMode(autowireMode);
return this;
}
public BeanDefinitionBuilder setDependencyCheck(int dependencyCheck) {
beanDefinition.setDependencyCheck(dependencyCheck);
return this;
}
public BeanDefinitionBuilder addDependsOn(String beanName) {
if (this.beanDefinition.getDependsOn() == null) {
this.beanDefinition.setDependsOn(beanName);
}
else {
String[] added = ObjectUtils.addObjectToArray(this.beanDefinition.getDependsOn(), beanName);
this.beanDefinition.setDependsOn(added);
}
return this;
}
public BeanDefinitionBuilder setRole(int role) {
this.beanDefinition.setRole(role);
return this;
}
}
