CommandLineRunner和ApplicationRunner
本文主要來自:https://blog.csdn.net/zongzhankui/article/details/78681942
前言:
Spring Boot如何解決專案啟動時初始化資源,在我們實際工作中,總會遇到這樣需求,在專案啟動的時候需要做一些初始化的操作,比如初始化執行緒池,提前載入好加密證書等。
為了達到這個目的,我們需要使用CommandLineRunner或ApplicationRunner介面建立bean,spring boot會自動監測到它們。這兩個介面都有一個run()方法,在實現介面時需要覆蓋該方法,並使用@Component註解使其成為bean。
CommandLineRunner和ApplicationRunner的作用是相同的。不同之處在於CommandLineRunner介面的run()方法接收String陣列作為引數,即是最原始的引數,沒有做任何處理;而ApplicationRunner介面的run()方法接收ApplicationArguments物件作為引數,是對原始引數做了進一步的封裝。
當程式啟動時,我們傳給main()方法的引數可以被實現CommandLineRunner和ApplicationRunner介面的類的run()方法訪問,即可接收啟動服務時傳過來的引數。我們可以建立多個實現CommandLineRunner和ApplicationRunner介面的類。為了使他們按一定順序執行,可以使用@Order註解或實現Ordered介面。
Maven配置
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.concretepage</groupId> <artifactId>spring-boot-demo</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>spring-demo</name> <description>Spring Boot Demo Project</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.2.RELEASE</version> </parent> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
CommandLineRunner:
run(String... args)
引數為String陣列。
CommandLineRunnerBean.java:
import java.util.Arrays;
import java.util.stream.Collectors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Component
public class CommandLineRunnerBean implements CommandLineRunner {
private static final Logger logger = LoggerFactory.getLogger(CommandLineRunnerBean.class);
@Override
public void run(String... args) {
String strArgs = Arrays.stream(args).collect(Collectors.joining("|"));
logger.info("Application started with arguments:" + strArgs);
}
}
MyApplication.java:
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import com.concretepage.service.HelloService;
@SpringBootApplication
public class MyApplication {
private static final Logger logger = LoggerFactory.getLogger(MyApplication.class);
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(MyApplication.class, args);
HelloService service = context.getBean(HelloService.class);
logger.info(service.getMessage());
}
}
我們也可以建立一個service。一旦Spring boot啟動完成service就會執行。這意味著SpringApplication.run()執行完成後service的方法就會執行。
HelloService.java:
import org.springframework.stereotype.Service;
@Service
public class HelloService {
public String getMessage(){
return "Hello World!";
}
}
現在使用帶有引數的可執行jar執行程式。spring-boot-demo-0.0.1-SNAPSHOT.jar為生成的jar檔案。執行命令如下:
java -jar spring-boot-demo-0.0.1-SNAPSHOT.jar data1 data2 data3
輸出結果為:
2017-03-19 13:38:38.909 INFO 1036 --- [ main] c.c.bean.CommandLineRunnerBean : Application started with arguments:data1|data2|data3
2017-03-19 13:38:38.914 INFO 1036 --- [ main] com.concretepage.MyApplication : Started MyApplication in 1.398 seconds (JVM running for 1.82)
2017-03-19 13:38:38.915 INFO 1036 --- [ main] com.concretepage.MyApplication : Hello World!
ApplicationRunner:
run(ApplicationArguments args)
可以看到,CommandLineRunner.run()接收String陣列作為引數,而ApplicationRunner.run()接收ApplicationArguments作為引數。這些引數是啟動spring boot程式時傳給main()方法的。
ApplicationRunnerBean.java:
import java.util.Arrays;
import java.util.stream.Collectors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;
@Component
public class ApplicationRunnerBean implements ApplicationRunner {
private static final Logger logger = LoggerFactory.getLogger(ApplicationRunnerBean.class);
@Override
public void run(ApplicationArguments arg0) throws Exception {
String strArgs = Arrays.stream(arg0.getSourceArgs()).collect(Collectors.joining("|"));
logger.info("Application started with arguments:" + strArgs);
}
}
建立可執行jar包並使用如下引數執行:
java -jar spring-boot-demo-0.0.1-SNAPSHOT.jar data1 data2 data3
輸出結果為:
2017-03-19 16:26:06.952 INFO 5004 --- [ main] c.c.bean.ApplicationRunnerBean : Application started with arguments:data1|data2|data3
2017-03-19 16:26:06.956 INFO 5004 --- [ main] com.concretepage.MyApplication : Started MyApplication in 1.334 seconds (JVM running for 1.797)
2017-03-19 16:26:06.957 INFO 5004 --- [ main] com.concretepage.MyApplication : Hello World!
ApplicationArguments是對引數(main方法)做了進一步的處理,可以解析–name=value的,我們就可以通過name來獲取value(而CommandLineRunner只是獲取–name=value),可以接收–foo=bar這樣的引數。
–getOptionNames()方法可以得到foo這樣的key的集合。
–getOptionValues(String name)方法可以得到bar這樣的集合的value。
看一個demo:
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;
import java.util.Arrays;
@Component
public class MyApplicationRunner implements ApplicationRunner{
@Override
public void run(ApplicationArguments args) throws Exception {
System.out.println("===MyApplicationRunner==="+ Arrays.asList(args.getSourceArgs()));
System.out.println("===getOptionNames========"+args.getOptionNames());
System.out.println("===getOptionValues======="+args.getOptionValues("foo"));
System.out.println("==getOptionValues========"+args.getOptionValues("developer.name"));
}
}
配置引數啟動:
執行結果:
===MyApplicationRunner===[--foo=bar, --developer.name=xiao.qiang]
===getOptionNames========[foo, developer.name]
===getOptionValues=======[bar]
==getOptionValues========[xiao.qiang]
CommandLineRunner和ApplicationRunner的執行順序:
在spring boot程式中,我們可以使用不止一個實現CommandLineRunner和ApplicationRunner的bean。為了有序執行這些bean的run()方法,可以使用@Order註解或Ordered介面。例子中我們建立了兩個實現CommandLineRunner介面的bean和兩個實現ApplicationRunner介面的bean。我們使用@Order註解按順序執行這四個bean。
CommandLineRunnerBean1.java
@Component
@Order(1)
public class CommandLineRunnerBean1 implements CommandLineRunner {
@Override
public void run(String... args) {
System.out.println("CommandLineRunnerBean 1");
}
}
ApplicationRunnerBean1.java
@Component
@Order(2)
public class ApplicationRunnerBean1 implements ApplicationRunner {
@Override
public void run(ApplicationArguments arg0) throws Exception {
System.out.println("ApplicationRunnerBean 1");
}
}
CommandLineRunnerBean2.java
@Component
@Order(3)
public class CommandLineRunnerBean2 implements CommandLineRunner {
@Override
public void run(String... args) {
System.out.println("CommandLineRunnerBean 2");
}
}
ApplicationRunnerBean2.java
@Component
@Order(4)
public class ApplicationRunnerBean2 implements ApplicationRunner {
@Override
public void run(ApplicationArguments arg0) throws Exception {
System.out.println("ApplicationRunnerBean 2");
}
}
輸出結果為:
CommandLineRunnerBean 1
ApplicationRunnerBean 1
CommandLineRunnerBean 2
ApplicationRunnerBean 2