springboot获取applicationcontext

灰太狼 2023-02-23 14:28 19阅读 0赞

题记：

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.

总结：

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

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3c4OTM5MzI3NDc_size_16_color_FFFFFF_t_70][]

查看run方法，发现该方法返回ConfigurableApplicationContext

![20200707212112314.png][]

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

![20200707212155236.png][]

1，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();
        }
    }

2，**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);
        }
    }

3，测试Bean

package com.demo.Demo001;
    
    import org.springframework.stereotype.Component;
    
    @Component
    public class TestBean {
        public String getName() {
            return this.getClass().getCanonicalName();
        }
    }

4，业务入口

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());
        }
    }

5，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

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3c4OTM5MzI3NDc_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/2020070721202819.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3c4OTM5MzI3NDc=,size_16,color_FFFFFF,t_70
[20200707212112314.png]: https://img-blog.csdnimg.cn/20200707212112314.png
[20200707212155236.png]: https://img-blog.csdnimg.cn/20200707212155236.png