package com.arhorchin.securitit.initbean;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;

/**
 * @author Securitit.
 * @note Bean初始化測試.
 */
public class InitTestBean implements InitializingBean {

    /**
     * logger.
     */
    private Logger logger = LoggerFactory.getLogger(InitTestBean.class);
    
    @Override
    public void afterPropertiesSet() throws Exception {
        logger.info("調(diào)用InitializingBean的afterPropertiesSet方法.");
    }
    
    public void initMethod() throws Exception {
        logger.info("調(diào)用init-method的initMethod方法.");
    }

}

<bean class="com.arhorchin.securitit.initbean.InitTestBean" init-method="initMethod"></bean>

/**
 * 初始化給定的Bean實(shí)例，應(yīng)用工廠回調(diào)、init方法和Bean后處理程序.
 * 對于傳統(tǒng)定義的Bean，從createBean調(diào)用，對于現(xiàn)有的Bean實(shí)例從initializeBean調(diào)用.
 * @param beanName 工廠中的Bean名稱（用于調(diào)試）.
 * @param bean 需要初始化新的Bean實(shí)例.
 * @param mbd 創(chuàng)建Bean時(shí)使用的Bean定義（如果給定現(xiàn)有的Bean實(shí)例，也可以是null）.
 * @return 初始化的Bean實(shí)例（可能被包裝）.
 */
protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
    // 若Bean實(shí)現(xiàn)了Aware接口，則觸發(fā)方法調(diào)用.
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
            invokeAwareMethods(beanName, bean);
            return null;
        }, getAccessControlContext());
    }
    else {
        invokeAwareMethods(beanName, bean);
    }

    Object wrappedBean = bean;
    // 在Bean初始化前處理BeanPostProcessor.
    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    }
    // 進(jìn)行Bean初始化，包括如下兩種方式：
    // 1.調(diào)用InitializingBean.afterPropertiesSet()方法.
    // 2.調(diào)用Bean配置的init-method方法.
    try {
        invokeInitMethods(beanName, wrappedBean, mbd);
    }
    catch (Throwable ex) {
        throw new BeanCreationException(
            (mbd != null ? mbd.getResourceDescription() : null),
            beanName, "Invocation of init method failed", ex);
    }
    // 在Bean初始化后處理BeanPostProcessor.
    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    }

    return wrappedBean;
}

/**
 * 若Bean實(shí)現(xiàn)了Aware接口，則觸發(fā)方法調(diào)用.
 */
private void invokeAwareMethods(final String beanName, final Object bean) {
    if (bean instanceof Aware) {
        // 調(diào)用BeanNameAware.setBeanName(...)方法.
        if (bean instanceof BeanNameAware) {
            ((BeanNameAware) bean).setBeanName(beanName);
        }
        // 調(diào)用BeanClassLoaderAware.setBeanClassLoader(...)方法.
        if (bean instanceof BeanClassLoaderAware) {
            ClassLoader bcl = getBeanClassLoader();
            if (bcl != null) {
                ((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
            }
        }
        // 調(diào)用BeanFactoryAware.setBeanFactory(...).
        if (bean instanceof BeanFactoryAware) {
            ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
        }
    }
}

/**
 * 所有屬性設(shè)置完成后可選的Bean初始化.
 * Bean實(shí)現(xiàn)了InitializingBean接口或定義了init-method方法，則會進(jìn)行回調(diào)處理.
 * @param beanName 工廠中的Bean名稱（用于調(diào)試）.
 * @param bean 需要初始化新的Bean實(shí)例.
 * @param mbd 創(chuàng)建Bean時(shí)使用的合并Bean定義（如果給定現(xiàn)有的Bean實(shí)例，也可以是null）.
 */
protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
    throws Throwable {
    // Bean是否實(shí)現(xiàn)了InitializingBean接口.
    boolean isInitializingBean = (bean instanceof InitializingBean);
    // 調(diào)用InitializingBean.afterPropertiesSet()方法.需要滿足條件：
    // 1.Bean實(shí)現(xiàn)了InitializingBean接口.
    // 2.Bean為空或afterPropertiesSet方法未被@PostConstruct注釋.
    if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
        if (logger.isDebugEnabled()) {
            logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
        }
        // 調(diào)用InitializingBean.afterPropertiesSet()方法.
        if (System.getSecurityManager() != null) {
            try {
                AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
                    ((InitializingBean) bean).afterPropertiesSet();
                    return null;
                }, getAccessControlContext());
            }
            catch (PrivilegedActionException pae) {
                throw pae.getException();
            }
        }
        else {
            ((InitializingBean) bean).afterPropertiesSet();
        }
    }
    // 調(diào)用配置init-method方法處理.
    if (mbd != null && bean.getClass() != NullBean.class) {
        String initMethodName = mbd.getInitMethodName();
        // 1.init-method配置不能為空.
        // 2.Bean不能實(shí)現(xiàn)InitializingBean或init-method方法不是afterPropertiesSet.
        // 3.init-method方法未被@PostConstruct注釋.
        if (StringUtils.hasLength(initMethodName) &&
            !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
            !mbd.isExternallyManagedInitMethod(initMethodName)) {
            invokeCustomInitMethod(beanName, bean, mbd);
        }
    }
}

/**
 * 在給定的Bean上調(diào)用指定的自定義init方法.由invokeInitMethods調(diào)用.
 * 可以在子類中重寫，以便使用參數(shù)自定義解析init方法.
 */
protected void invokeCustomInitMethod(String beanName, final Object bean, RootBeanDefinition mbd)
    throws Throwable {
    // 取得Method實(shí)例.
    String initMethodName = mbd.getInitMethodName();
    Assert.state(initMethodName != null, "No init method set");
    final Method initMethod = (mbd.isNonPublicAccessAllowed() ?
                               BeanUtils.findMethod(bean.getClass(), initMethodName) :
                               ClassUtils.getMethodIfAvailable(bean.getClass(), initMethodName));
    if (initMethod == null) {
        if (mbd.isEnforceInitMethod()) {
            throw new BeanDefinitionValidationException("Couldn't find an init method named '" +
                                                        initMethodName + "' on bean with name '" + beanName + "'");
        }
        else {
            if (logger.isDebugEnabled()) {
                logger.debug("No default init method named '" + initMethodName +
                             "' found on bean with name '" + beanName + "'");
            }
            // Ignore non-existent default lifecycle methods.
            return;
        }
    }
    if (logger.isDebugEnabled()) {
        logger.debug("Invoking init method  '" + initMethodName + "' on bean with name '" + beanName + "'");
    }
    // 調(diào)用Bean的init-method配置的方法.
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
            ReflectionUtils.makeAccessible(initMethod);
            return null;
        });
        try {
            AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
                                          initMethod.invoke(bean), getAccessControlContext());
        }
        catch (PrivilegedActionException pae) {
            InvocationTargetException ex = (InvocationTargetException) pae.getException();
            throw ex.getTargetException();
        }
    }
    else {
        try {
            ReflectionUtils.makeAccessible(initMethod);
            initMethod.invoke(bean);
        }
        catch (InvocationTargetException ex) {
            throw ex.getTargetException();
        }
    }
}