在容器启动完成时，继承 CommandLineRunner 接口的类的 run 方法会被自动执行（前提是这个类被Spring 管理）。
入门
示例代码结构：
demo01
├── build.gradle
└── src
├── main
│ ├── java
│ │ └── demo
│ │ ├── CustomCommandLineRunner.java
│ │ └── Demo01Application.java
│ └── resources
└── test
├── java
└── resources
build.gradle 内容：
buildscript {
ext {
springBootVersion = '2.1.3.RELEASE'
}
repositories {
maven { url 'http://mirrors.cloud.tencent.com/nexus/repository/maven-public/' }
mavenCentral()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
}
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
repositories {
maven { url 'http://mirrors.cloud.tencent.com/nexus/repository/maven-public/' }
mavenCentral()
}
dependencies {
compile('org.springframework.boot:spring-boot-starter')
testCompile('org.springframework.boot:spring-boot-starter-test')
}
Demo01Application 内容：
package demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Demo01Application {
public static void main(String[] args) {
SpringApplication.run(Demo01Application.class, args);
}
}
CustomCommandLineRunner 内容：
package demo;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Component
public class CustomCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("This is CustomCommandLineRunner");
for (int i=0; i<args.length; ++i) {
System.out.printf("%d: %s\n", i, args[i]);
}
}
}
运行Demo01Application，会看到：
This is CustomCommandLineRunner
run 方法的args 是命令行参数，我们试下加上命令行参数运行。
命令行进入demo01目录：
$ gradle build
$ find . -name "*.jar"
./build/libs/demo01-0.0.1-SNAPSHOT.jar
执行jar包：
$ java -jar ./build/libs/demo01-0.0.1-SNAPSHOT.jar hello 123
This is CustomCommandLineRunner
0: hello
1: 123
多个 CommandLineRunner
可以用Order注解，指定执行顺序。
示例代码结构：
demo02
├── build.gradle
└── src
├── main
│ ├── java
│ │ └── demo
│ │ ├── CustomCommandLineRunner01.java
│ │ ├── CustomCommandLineRunner02.java
│ │ └── Demo02Application.java
│ └── resources
└── test
├── java
└── resources
CustomCommandLineRunner01 内容：
package demo;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
@Order(1) // 值越小，越先执行
public class CustomCommandLineRunner01 implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("This is CustomCommandLineRunner01");
for (int i=0; i<args.length; ++i) {
System.out.printf("%d: %s\n", i, args[i]);
}
}
}
CustomCommandLineRunner02 内容：
package demo;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
@Order(0) // 值越小，越先执行
public class CustomCommandLineRunner02 implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("This is CustomCommandLineRunner02");
for (int i=0; i<args.length; ++i) {
System.out.printf("%d: %s\n", i, args[i]);
}
}
}
如果去掉Order注解，Demo02Application运行结果是：
This is CustomCommandLineRunner02
This is CustomCommandLineRunner01
不去掉Order注解，Demo02Application运行结果是：
This is CustomCommandLineRunner01
This is CustomCommandLineRunner02
Order 中的值越小，越先执行。
@SpringBootApplication 与 CommandLineRunner 一起用
示例代码结构：
demo03
├── build.gradle
└── src
├── main
│ ├── java
│ │ └── demo
│ │ ├── Demo03Application.java
│ │ └── SayHello.java
│ └── resources
└── test
├── java
└── resources
SayHello 内容：
package demo;
import org.springframework.stereotype.Component;
@Component
public class SayHello {
public String sayHello(String msg) {
return "Hello " + msg;
}
}
Demo03Application 内容：
package demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Component;
@SpringBootApplication
@Component
public class Demo03Application implements CommandLineRunner {
@Autowired
private SayHello sayHello;
public static void main(String[] args) {
SpringApplication.run(Demo03Application.class, args);
}
@Override
public void run(String... args) throws Exception {
System.out.println("This is Demo03Application");
System.out.println(sayHello.sayHello("World"));
}
}
运行 Demo03Application，输出：
This is Demo03Application
Hello World