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這篇文章主要講解了“Spring核心接口InitializingBean怎么應(yīng)用”,文中的講解內(nèi)容簡單清晰,易于學(xué)習(xí)與理解,下面請大家跟著小編的思路慢慢深入,一起來研究和學(xué)習(xí)“Spring核心接口InitializingBean怎么應(yīng)用”吧!
一、InitializingBean接口說明
InitializingBean接口為bean提供了屬性初始化后的處理方法,它只包括afterPropertiesSet方法,凡是繼承該接口的類,在bean的屬性初始化后都會執(zhí)行該方法。
package org.springframework.beans.factory;
/**
* Interface to be implemented by beans that need to react once all their
* properties have been set by a BeanFactory: for example, to perform custom
* initialization, or merely to check that all mandatory properties have been set.
*
* <p>An alternative to implementing InitializingBean is specifying a custom
* init-method, for example in an XML bean definition.
* For a list of all bean lifecycle methods, see the BeanFactory javadocs.
*
* @author Rod Johnson
* @see BeanNameAware
* @see BeanFactoryAware
* @see BeanFactory
* @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
* @see org.springframework.context.ApplicationContextAware
*/
public interface InitializingBean {
/**
* Invoked by a BeanFactory after it has set all bean properties supplied
* (and satisfied BeanFactoryAware and ApplicationContextAware).
* <p>This method allows the bean instance to perform initialization only
* possible when all bean properties have been set and to throw an
* exception in the event of misconfiguration.
* @throws Exception in the event of misconfiguration (such
* as failure to set an essential property) or if initialization fails.
*/
void afterPropertiesSet() throws Exception;
}
從方法名afterPropertiesSet也可以清楚的理解該方法是在屬性設(shè)置后才調(diào)用的。
二、源碼分析接口應(yīng)用
通過查看spring的加載bean的源碼類(AbstractAutowireCapableBeanFactory)可以看到
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
//判斷該bean是否實現(xiàn)了實現(xiàn)了InitializingBean接口,如果實現(xiàn)了InitializingBean接口,則調(diào)用bean的afterPropertiesSet方法
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isDebugEnabled()) {
logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
public Object run() throws Exception {
//調(diào)用afterPropertiesSet
((InitializingBean) bean).afterPropertiesSet();
return null;
}
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
//調(diào)用afterPropertiesSet
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null) { //判斷是否指定了init-method方法,如果指定了init-method方法,則再調(diào)用制定的init-method
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
//反射調(diào)用init-method方法
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
分析代碼可以了解:
1:spring為bean提供了兩種初始化bean的方式,實現(xiàn)InitializingBean接口,實現(xiàn)afterPropertiesSet方法,或者在配置文件中同過init-method指定,兩種方式可以同時使用
2:實現(xiàn)InitializingBean接口是直接調(diào)用afterPropertiesSet方法,比通過反射調(diào)用init-method指定的方法效率相對來說要高點。但是init-method方式消除了對spring的依賴
3:如果調(diào)用afterPropertiesSet方法時出錯,則不調(diào)用init-method指定的方法。
三、接口應(yīng)用
InitializingBean接口在spring框架中本身就很多應(yīng)用,這就不多說了。我們在實際應(yīng)用中如何使用該接口呢?
1、使用InitializingBean接口處理一個配置文件:
import java.io.File;
import java.io.FileInputStream;
import java.util.Properties;
import org.springframework.beans.factory.InitializingBean;
public class ConfigBean implements InitializingBean{
//微信公眾號配置文件
private String configFile;
private String appid;
private String appsecret;
public String getConfigFile() {
return configFile;
}
public void setConfigFile(String configFile) {
this.configFile = configFile;
}
public void afterPropertiesSet() throws Exception {
if(configFile!=null){
File cf = new File(configFile);
if(cf.exists()){
Properties pro = new Properties();
pro.load(new FileInputStream(cf));
appid = pro.getProperty("wechat.appid");
appsecret = pro.getProperty("wechat.appsecret");
}
}
System.out.println(appid);
System.out.println(appsecret);
}
}
2、配置
spring配置文件:
<bean id="configBean" class="com.ConfigBean">
<property name="configFile" value="d:/wechat.properties"></property>
</bean>
wechat.properties配置文件
wechat.appid=wxappid
wechat.appsecret=wxappsecret
3、測試
public static void main(String[] args) throws Exception {
String config = Test.class.getPackage().getName().replace('.', '/') + "/bean.xml";
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(config);
context.start();
}
感謝各位的閱讀,以上就是“Spring核心接口InitializingBean怎么應(yīng)用”的內(nèi)容了,經(jīng)過本文的學(xué)習(xí)后,相信大家對Spring核心接口InitializingBean怎么應(yīng)用這一問題有了更深刻的體會,具體使用情況還需要大家實踐驗證。這里是億速云,小編將為大家推送更多相關(guān)知識點的文章,歡迎關(guān)注!
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