使用springboot之前，我们通过ClassPathXmlApplicationContext加载spring xml配置文件来获取applicationcontext，使用springboot后，由于不存在xml文件，故该种方式已经不能使用
在官方文档中介绍，可通过实现ApplicationRunner或者CommandLineRunner在springaplication启动后，立即执行其中的一些代码，做初始化操作，如果存在多个实现类，可使用@Order注解设置其启动顺序，也可使用实现ApplicationListener来做初始化操作，并且实现ApplicationListener可获取到applicationcontext
获取applicationcontext的方式有多种，以下列举出两种方式
一、实现ApplicationListener<ContextRefreshedEvent>
1、启动类
package com.demo.bootdemo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication; import com.demo.bootdemo.listeners.MainBusiListeners;
import com.demo.bootdemo.test.TestBean;
import com.demo.bootdemo.uitils.ApplicationContextUtils; @SpringBootApplication
public class MydemoApplication { public static void main(String[] args) {
SpringApplication sa = new SpringApplication(MydemoApplication.class);
sa.addListeners(new MainBusiListeners());
sa.run(args);
// 测试
TestBean bean = ApplicationContextUtils.getBean(TestBean.class);
bean.print("yes it is test.");
} }
2、启动监听
package com.demo.bootdemo.listeners; import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import com.demo.bootdemo.uitils.ApplicationContextUtils; /**
* 启动监听
*/
public class MainBusiListeners implements ApplicationListener<ContextRefreshedEvent> {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
ApplicationContextUtils.setContext(event.getApplicationContext());
}
}
3、ApplicationContext工具类
package com.demo.bootdemo.uitils; import org.springframework.context.ApplicationContext; /**
* ApplicaitonContext工具类
*
*/
public class ApplicationContextUtils { private static ApplicationContext context; public static void setContext(ApplicationContext applicationContext) {
context = applicationContext;
} public static Object getBean(String beanName) {
return context.getBean(beanName);
} public static <T> T getBean(Class<T> t) {
return context.getBean(t);
}
}
4、测试Bean
package com.demo.bootdemo.test; import org.springframework.stereotype.Component; /**
* 测试Bean
*/
@Component
public class TestBean { public void print(String str) {
System.out.println("input: " + str);
}
}
5、启动启动类MydemoApplication.java
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.3.RELEASE) 2019-04-04 09:51:28.722 INFO 93344 --- [ main] com.demo.bootdemo.MydemoApplication : Starting MydemoApplication on admin-PC with PID 93344 (D:\Programs\eclipseworkplace\springboot\mydemo\target\classes started by admin in D:\Programs\eclipseworkplace\springboot\mydemo)
2019-04-04 09:51:28.725 INFO 93344 --- [ main] com.demo.bootdemo.MydemoApplication : No active profile set, falling back to default profiles: default
2019-04-04 09:51:29.247 INFO 93344 --- [ main] com.demo.bootdemo.MydemoApplication : Started MydemoApplication in 0.838 seconds (JVM running for 1.204)
input: yes it is test.
通过上述输出结果可知，applicationcontext正常获取，如果需要在run方法执行之前，使用applicationcontext做一些事情，可在MainBusiListeners的onApplicationEvent方法中进行。另外，使用@Component或者具有类似功能注解，启动类中去掉sa.addListeners(new MainBusiListeners());，一样可以正常获取applicationcontext，ApplicationListener中的Event有多种，父接口为ApplicationEvent，具体可参考源码查看
二、启动类run方法返回值即为applicationcontext
查看main方法中启动类代码
查看run方法，发现该方法返回ConfigurableApplicationContext
查看ConfigurableApplicationContext
接口实现了ApplicaitonContext接口，所以run方法返回的值就是我们需要的context了
启动类
package com.demo.Demo001; import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext; @SpringBootApplication
public class App {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
ContextUtils.setApplicationContext(context);
MainBusiEntry.execute();
}
}
context工具类
package com.demo.Demo001;
import org.springframework.context.ApplicationContext;
public class ContextUtils {
public static ApplicationContext context;
private ContextUtils() {
}
public static void setApplicationContext(ApplicationContext applicationContext) {
context = applicationContext;
}
public static Object getBean(String beanName) {
return context.getBean(beanName);
}
public static <T> T getBean(Class<T> t) {
return context.getBean(t);
}
}
测试bean
package com.demo.Demo001; import org.springframework.stereotype.Component; @Component
public class TestBean {
public String getName() {
return this.getClass().getCanonicalName();
}
}
业务处理入口
package com.demo.Demo001; import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger; public class MainBusiEntry { private static Logger logger = LogManager.getLogger(MainBusiEntry.class);
public static void execute() {
TestBean bean = ContextUtils.getBean(TestBean.class);
logger.info(bean.getName());
}
}
启动springboot，输出结果如下
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.0.RELEASE) 11:53:25.302 INFO org.springframework.boot.StartupInfoLogger.logStarting()/50 - Starting App on admin-PC with PID 195640 (D:\Programs\eclipseworkplace\springboot\Demo001\target\classes started by admin in D:\Programs\eclipseworkplace\springboot\Demo001)
11:53:25.338 INFO org.springframework.boot.SpringApplication.logStartupProfileInfo()/675 - No active profile set, falling back to default profiles: default
11:53:26.375 INFO com.mongodb.diagnostics.logging.SLF4JLogger.info()/71 - Cluster created with settings {hosts=[localhost:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
11:53:26.456 INFO org.springframework.boot.StartupInfoLogger.logStarted()/59 - Started App in 1.393 seconds (JVM running for 2.078)
11:53:26.459 INFO com.demo.Demo001.MainBusiEntry.execute()/11 - com.demo.Demo001.TestBean
输出了测试类的路径。
我们在开发中，使用的为第一种获取applicationcontext的方式