（011）Spring Boot之回调接口ApplicationContextInitializer、CommandLineRunner、ApplicationRunner

2022-02-16 13:11:39

　　ApplicationContextInitializer接口在spring容器执行refreshed之前回调，实现方式有3种

　　方式一：调用SpringApplication的addInitializers方法注册

　　pom.xml

（011）Spring Boot之回调接口ApplicationContextInitializer、CommandLineRunner、ApplicationRunner

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.edu.spring</groupId>
    <artifactId>springboot</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>springboot</name>
    <!-- FIXME change it to the project‘s website -->
    <url>http://www.example.com</url>
    
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.1.6.RELEASE</version>
                <scope>import</scope>
                <type>pom</type>
            </dependency>
        </dependencies>
    </dependencyManagement>
    
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
    </dependencies>

</project>

View Code

　　MyApplicationContextInitializer.java，实现ApplicationContextInitializer接口

package com.edu.spring.springboot;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

public class MyApplicationContextInitializer implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        // TODO Auto-generated method stub
        System.out.println("当前容器bean数量："+applicationContext.getBeanDefinitionCount());
    }

}

View Code

　　App.java，调用SpringApplication的addInitializers方法（可以有多个）

package com.edu.spring.springboot;

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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        app.addInitializers(new MyApplicationContextInitializer());
        ConfigurableApplicationContext context= app.run(args);
        context.close();
    }
}

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　　运行结果如下：

　　方式二：application.properties中配置context.initializer.classes属性（可以配置多个）

　　application.properties

context.initializer.classes=com.edu.spring.springboot.MyApplicationContextInitializer,com.edu.spring.springboot.MyApplicationContextInitializer2

View Code

　　MyApplicationContextInitializer2.java

package com.edu.spring.springboot;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

public class MyApplicationContextInitializer2 implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        // TODO Auto-generated method stub
        System.out.println("app name："+applicationContext.getApplicationName());
    }

}

View Code

　　App.java，去掉addInitializers方法

package com.edu.spring.springboot;

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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        ConfigurableApplicationContext context= app.run(args);
        context.close();
    }
}

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　　运行结果如下：

　　方式三：使用spring.factories机制

　　resources/META-INF/spring.factories

org.springframework.context.ApplicationContextInitializer=com.edu.spring.springboot.EchoApplicationContextInitializer

View Code

　　EchoApplicationContextInitializer.java

package com.edu.spring.springboot;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

public class EchoApplicationContextInitializer implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {

    public void initialize(ConfigurableApplicationContext applicationContext) {
        System.out.println("=============EchoApplicationContextInitializer=================");        
    }

}

View Code

　　App.java

package com.edu.spring.springboot;

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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        ConfigurableApplicationContext context= app.run(args);
        context.close();
    }
}

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　　运行结果如下：

　　由于spring.factories机制会扫描所有工程里面的/META-INF/spring.factories文件，所以另建一个工程也可以运行，如下：

　　新建core-bean

　　pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.edu.core</groupId>
    <artifactId>core-bean</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>springboot</name>
    <!-- FIXME change it to the project‘s website -->
    <url>http://www.example.com</url>
    
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
    </dependencies>

</project>

View Code

　　EchoApplicationContextInitializer.java

package com.edu.initializer;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

public class EchoApplicationContextInitializer implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {

    public void initialize(ConfigurableApplicationContext applicationContext) {
        System.out.println("=============core-bean:EchoApplicationContextInitializer=================");        
    }

}

View Code

　　resources/META-INF/spring.factories

org.springframework.context.ApplicationContextInitializer=com.edu.initializer.EchoApplicationContextInitializer

View Code

　　原工程的pom.xml文件引入core-bean坐标

　　pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.edu.spring</groupId>
    <artifactId>springboot</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>springboot</name>
    <!-- FIXME change it to the project‘s website -->
    <url>http://www.example.com</url>
    
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.1.6.RELEASE</version>
                <scope>import</scope>
                <type>pom</type>
            </dependency>
        </dependencies>
    </dependencyManagement>
    
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.edu.core</groupId>
            <artifactId>core-bean</artifactId>
            <version>1.0.0</version>
        </dependency>
    </dependencies>

</project>

View Code

　　运行原工程App.java

package com.edu.spring.springboot;

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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        ConfigurableApplicationContext context= app.run(args);
        context.close();
    }
}

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　　运行结果如下：

　　CommandLineRunner、ApplicationRunner是spring容器启动成功后最后的回调，@Order控制顺序，数字越小越先执行，请看示例：

　　ServerSuccessReport.java

package com.edu.spring.springboot;

import java.util.Arrays;

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

@Order(1)
@Component
public class ServerSuccessReport implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        // TODO Auto-generated method stub
        System.out.println("==========ServerSuccessReport1============"+Arrays.asList(args));
    }

}

View Code

　　ServerSuccessReport2.java

package com.edu.spring.springboot;

import java.util.Arrays;

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

@Order(3)
@Component
public class ServerSuccessReport2 implements CommandLineRunner {

    @Override
    public void run(String... args) throws Exception {
        // TODO Auto-generated method stub
        System.out.println("==========ServerSuccessReport2============"+Arrays.asList(args));
    }

}

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　　StartedApplicationRunner.java

package com.edu.spring.springboot;

import java.util.Arrays;

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

@Order(2)
@Component
public class StartedApplicationRunner implements ApplicationRunner {

    public void run(ApplicationArguments args) throws Exception {
        System.out.println("应用已经启动，参数为："+Arrays.asList(args.getSourceArgs()));
    }

}

View Code

　　App.java

package com.edu.spring.springboot;

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 )
    {
        SpringApplication app=new SpringApplication(App.class);
        ConfigurableApplicationContext context= app.run("aa","bb ");
        context.close();
    }
}

View Code

　　运行结果如下：

　　CommandLineRunner与ApplicationRunner的区别是CommandLineRunner参数是原始的，ApplicationRunner参数是对原始参数的封装。

（011）Spring Boot之回调接口ApplicationContextInitializer、CommandLineRunner、ApplicationRunner

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