<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"><property name="entityManagerFactory" ref="entityManagerFactory" /></bean>

    /*** Generate a bean name for the given bean definition.* 根据给定的bean definition 生成一个bean的名字* @param definition the bean definition to generate a name for* @param 参数 definition 需要生成bean name的BeanDefinition实例* @param registry the bean definition registry that the given definition* is supposed to be registered with* @param 参数registry 是 definition 注册* @return the generated bean name* @return 返回生成的bean name*/String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry);

    /*** Generate a bean name for the given top-level bean definition,    * unique within the given bean factory.* @param beanDefinition the bean definition to generate a bean name for* @param registry the bean factory that the definition is going to be* registered with (to check for existing bean names)* @return the generated bean name* @throws BeanDefinitionStoreException if no unique name can be generated* for the given bean definition*/public static String generateBeanName(BeanDefinition beanDefinition, BeanDefinitionRegistry registry)throws BeanDefinitionStoreException {return generateBeanName(beanDefinition, registry, false);}

/*** Generate a bean name for the given bean definition, unique within the* given bean factory.* @param definition the bean definition to generate a bean name for* @param registry the bean factory that the definition is going to be* registered with (to check for existing bean names)* @param isInnerBean whether the given bean definition will be registered* as inner bean or as top-level bean (allowing for special name generation* for inner beans versus top-level beans)    * @param isInnerBean  参数definition会被注册为一个内部bean还是一个顶级bean(内部bean和顶级bean 都允许使用特殊名字定义）* @return the generated bean name* @throws BeanDefinitionStoreException if no unique name can be generated* for the given bean definition* @throws BeanDefinitionStoreException 当没有唯一的名称可供生成的时候抛出异常*/public static String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry, boolean isInnerBean)throws BeanDefinitionStoreException {//generatedBeanName定义为类前缀， 读取bean的className,不一定是运行时的实际类型。String generatedBeanName = definition.getBeanClassName();if (generatedBeanName == null) {//如果类名称为空，那读取bean的parent bean name if (definition.getParentName() != null) {generatedBeanName = definition.getParentName() + "$child";}//否则，读取生成该bean的factoryBean name名称做前缀。else if (definition.getFactoryBeanName() != null) {generatedBeanName = definition.getFactoryBeanName() + "$created";}}//generatedBeanName为空字符串，抛出异常if (!StringUtils.hasText(generatedBeanName)) {throw new BeanDefinitionStoreException("Unnamed bean definition specifies neither " +"'class' nor 'parent' nor 'factory-bean' - can't generate bean name");}String id = generatedBeanName;//当为内部bean时，调用系统底层的object唯一标识码生成if (isInnerBean) {// Inner bean: generate identity hashcode suffix. id = generatedBeanName + GENERATED_BEAN_NAME_SEPARATOR + ObjectUtils.getIdentityHexString(definition);}//否则即为顶级bean，生成策略是前缀+循环数字，直到找到对应自增idelse {// Top-level bean: use plain class name.// Increase counter until the id is unique.int counter = -1;while (counter == -1 || registry.containsBeanDefinition(id)) {counter++;id = generatedBeanName + GENERATED_BEAN_NAME_SEPARATOR + counter;}}return id;}

//    ObjectUtils.java/*** Return a hex String form of an object's identity hash code.* 返回一个十六进制数从hash code中获得* @param obj*            the object* @return the object's identity code in hex notation*/public static String getIdentityHexString(Object obj) {return Integer.toHexString(System.identityHashCode(obj));}//    System.java/*** Returns the same hash code for the given object as would be returned by* the default method hashCode(), whether or not the given object's class* overrides hashCode(). The hash code for the null reference is zero.* * @param x*            object for which the hashCode is to be calculated* @return the hashCode* @since JDK1.1*///native 表示操作系统实现的底层框架，用于生成对象的hashcode。jvm的实现还没有关心。public static native int identityHashCode(Object x);//  Integer.java/*** All possible chars for representing a number as a String*/final static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8','9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l','m', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y','z' };public static String toHexString(int i) {return toUnsignedString(i, 4);}private static String toUnsignedString(int i, int shift) {char[] buf = new char[32];int charPos = 32;int radix = 1 << shift;int mask = radix - 1;do {buf[--charPos] = digits[i & mask];i >>>= shift;} while (i != 0);return new String(buf, charPos, (32 - charPos));}