springBoot学习（四）项目初始化的开始和结束

杨小杰

发布于 2019-07-04 08:26:26

86100

代码可运行

文章被收录于专栏：JAVA知识总结与分享JAVA知识总结与分享

运行总次数：0

代码可运行

ApplicationContextInitializer接口

用来初始化Spring ConfigurableApplicationContext应用上下文的回调接口，是在ConfigurableApplicationContext.refresh()之前调用。该接口典型的应用场景是web应用中需要编程方式对应用上下文做初始化。比如，注册属性源(property sources)或者针对上下文的环境信息environment激活相应的profile

代码实现

默认的application.properties文件(默认指定为生产环境)

test.name=default
spring.profiles.active=prd

application-dev.properties文件

test.name=dev

application-prd.properties文件

test.name=prd

自定义MyApplicationContextInitializer实现ApplicationContextInitializer接口，重写initialize方法

package com.yxj.spring.Initializer;

import com.yxj.spring.SpringBootTestRun;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring.Initializer
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/25 22:39
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/25 22:39
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
public class MyApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

    /**
     * 1.springBoot执行ApplicationContextInitializer refresh方法之前会先执行
     * 2.在方法中设置活动配置文件为dev(该结果可以从其他途径去获取，这里给定默认值dev)
     * 3.在启动类最后获取name，查看最终结果
     * @param applicationContext
     */
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        applicationContext.getEnvironment().setActiveProfiles("dev");
        System.out.println("-------初始化---------");
    }
}

springBoot启动类

package com.yxj.spring;

import com.yxj.spring.Initializer.MyApplicationContextInitializer;
import com.yxj.spring.monitor.MyApplicationListener;
import com.yxj.spring.monitor.MyEvent;
import com.yxj.spring.properties.TestProperties;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Import;

import java.util.List;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/18 20:18
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/18 20:18
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@SpringBootApplication
public class SpringBootTestRun {

    @Value("${test.name}")
    private String testName;

    /**
     * 添加初始化类方式
     * 1.springBootTestRun.addInitializers(new MyApplicationContextInitializer());
     * 2.通过配置项来指定（context.initiallzer.classes=com.yxj.spring.Initializer.MyApplicationContextInitializer）
     * 3.spring.factories机制
     * 应用：
     * 当外部程序装配这个模块的时候，就能通过该jar包META-INF/services/里的配置文件找到具体的实现类名，并装载实例化，完成模块的注入
     * 在日常工作中，我们可能需要实现一些SDK或者Spring Boot Starter给被人使用，这个使用我们就可以使用Factories机制。
     * Factories机制可以让SDK或者Starter的使用只需要很少或者不需要进行配置，只需要在服务中引入我们的jar包。
     * 详细使用参考：http://blog.51cto.com/13836814/2134630
     *
     * @param args
     */
    public static void main(String[] args) {
        SpringApplication springBootTestRun = new SpringApplication(SpringBootTestRun.class);
        //springBootTestRun.addInitializers(new MyApplicationContextInitializer());
        ConfigurableApplicationContext run = springBootTestRun.run(args);
        SpringBootTestRun bean = run.getBean(SpringBootTestRun.class);
        System.out.println("------------分割线------------");
        System.out.println(bean.testName);
        run.close();
    }
}

测试结果

-------初始化---------


------------分割线------------
dev

CommandLineRunner和ApplicationRunner接口

CommandLineRunner、ApplicationRunner 接口是在容器启动成功后的最后一步回调。如果希望在项目启动完成之前，初始化一些操作，可以使用这两个接口。

实现

实现CommandLineRunner或者ApplicationRunner接口
实现run方法
通过@Component或者其他方式添加到spring容器管理中
可以实现多个，通过@Order(value = XXX)的方式，可以实现排序

CommandLineRunner接口

第一个CommandLineRunner

package com.yxj.spring.runner;

import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.Arrays;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring.runner
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/25 23:10
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/25 23:10
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@Component
@Order(value = 4)
public class MyCommandLineRunner1 implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("order value is 4   。MyCommandLineRunner1 run.  get args : "+Arrays.asList(args));
    }
}

第二个CommandLineRunner

package com.yxj.spring.runner;

import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.Arrays;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring.runner
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/25 23:10
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/25 23:10
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@Component
@Order(value = 1)
public class MyCommandLineRunner2 implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("order value is 1   。MyCommandLineRunner2 run.  get args : "+Arrays.asList(args));
    }
}

第一个ApplicationRunner

package com.yxj.spring.runner;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring.runner
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/25 23:27
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/25 23:27
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@Component
@Order(value = 3)
public class MyApplicationRunner1 implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        for(String argsString :args.getOptionNames()){
            System.out.println("order value is 3   。MyApplicationRunner1 is ApplicationArguments key : ("+argsString + ")   ApplicationArguments value : ("+args.getOptionValues(argsString)+")");
        }
    }
}

第二个ApplicationRunner

package com.yxj.spring.runner;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring.runner
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/25 23:27
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/25 23:27
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@Component
@Order(value = 2)
public class MyApplicationRunner2 implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        for(String argsString :args.getOptionNames()){
            System.out.println("order value is 2   。MyApplicationRunner2 is ApplicationArguments key : ("+argsString + ")   ApplicationArguments value : ("+args.getOptionValues(argsString)+")");
        }
    }
}

springBoot测试启动类

package com.yxj.spring;

import com.yxj.spring.Initializer.MyApplicationContextInitializer;
import com.yxj.spring.monitor.MyApplicationListener;
import com.yxj.spring.monitor.MyEvent;
import com.yxj.spring.properties.TestProperties;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Import;

import java.util.List;

/**
 * @ProjectName: springBootDemo
 * @Package: com.yxj.spring
 * @Description:
 * @Author: 阿杰
 * @CreateDate: 2019/1/18 20:18
 * @UpdateUser: 暂无
 * @UpdateDate: 2019/1/18 20:18
 * @UpdateRemark: The modified content
 * @Version: 1.0
 */
@SpringBootApplication
public class SpringBootTestRun {

    @Value("${test.name}")
    private String testName;

    public static void main(String[] args) {
        SpringApplication springBootTestRun = new SpringApplication(SpringBootTestRun.class);
        ConfigurableApplicationContext run = springBootTestRun.run("测试1","测试2","--key1=测试3","--key2=测试4");
        run.close();
    }
}

测试结果

order value is 1   。MyCommandLineRunner2 run.  get args : [测试1, 测试2, --key1=测试3, --key2=测试4]
order value is 2   。MyApplicationRunner2 is ApplicationArguments key : (key1)   ApplicationArguments value : ([测试3])
order value is 2   。MyApplicationRunner2 is ApplicationArguments key : (key2)   ApplicationArguments value : ([测试4])
order value is 3   。MyApplicationRunner1 is ApplicationArguments key : (key1)   ApplicationArguments value : ([测试3])
order value is 3   。MyApplicationRunner1 is ApplicationArguments key : (key2)   ApplicationArguments value : ([测试4])
order value is 4   。MyCommandLineRunner1 run.  get args : [测试1, 测试2, --key1=测试3, --key2=测试4]

对比

两个都是在容器启动成功后的最后一步回调
CommandLineRunner的参数是最原始的参数，没有做任何处理。ApplicationRunner的参数是ApplicationArguments，是对原始参数做了进一步的封装。
ApplicationRunner只对--key=value这种形式做解析，CommandLineRunner可以获得传递的所有字符串

本文参与腾讯云自媒体同步曝光计划，分享自微信公众号。

原始发表：2019-01-25，如有侵权请联系 cloudcommunity@tencent.com 删除

容器