Spring Boot生成的项目打印两次。

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英文:

Spring boot generated project printing twice

问题

POM:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.1.2</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example.demo</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>demo</name>
	<description>Demo project for Spring Boot</description>
	<properties>
		<java.version>17</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-groovy-templates</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-jdbc</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-thymeleaf</artifactId>
		</dependency>
		<dependency>
			<groupId>org.flywaydb</groupId>
			<artifactId>flyway-core</artifactId>
		</dependency>
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter</artifactId>
			<version>3.0.2</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
			<scope>runtime</scope>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-docker-compose</artifactId>
			<scope>runtime</scope>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.mybatis.spring.boot</groupId>
			<artifactId>mybatis-spring-boot-starter-test</artifactId>
			<version>3.0.2</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.jetbrains</groupId>
			<artifactId>annotations</artifactId>
			<version>RELEASE</version>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>jakarta.annotation</groupId>
			<artifactId>jakarta.annotation-api</artifactId>
			<version>1.3.5</version>
		</dependency>
		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-api</artifactId>
			<version>5.9.3</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.13.2</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
					<excludes>
						<exclude>
							<groupId>org.projectlombok</groupId>
							<artifactId>lombok</artifactId>
						</exclude>
					</excludes>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

Main:

package com.example.demo.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan(basePackages = "com.example.demo") // Add the package of your component
public class DemoApplication {

    public static void main(String[] args) {
        System.out.println("Demo");
        SpringApplication.run(DemoApplication.class, args);
    }
}

我通过这里获取了演示代码,但我不明白为什么会打印两次。我不理解这为什么会发生。我尝试创建一个不同的类,但该类没有被调用,所以尝试了这种方式。

英文:

POM:

&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
&lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot; xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd&quot;&gt;
&lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
&lt;parent&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-starter-parent&lt;/artifactId&gt;
&lt;version&gt;3.1.2&lt;/version&gt;
&lt;relativePath/&gt; &lt;!-- lookup parent from repository --&gt;
&lt;/parent&gt;
&lt;groupId&gt;com.example.demo&lt;/groupId&gt;
&lt;artifactId&gt;demo&lt;/artifactId&gt;
&lt;version&gt;0.0.1-SNAPSHOT&lt;/version&gt;
&lt;name&gt;demo&lt;/name&gt;
&lt;description&gt;Demo project for Spring Boot&lt;/description&gt;
&lt;properties&gt;
&lt;java.version&gt;17&lt;/java.version&gt;
&lt;/properties&gt;
&lt;dependencies&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-starter-groovy-templates&lt;/artifactId&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-starter-jdbc&lt;/artifactId&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-starter-thymeleaf&lt;/artifactId&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.flywaydb&lt;/groupId&gt;
&lt;artifactId&gt;flyway-core&lt;/artifactId&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.mybatis.spring.boot&lt;/groupId&gt;
&lt;artifactId&gt;mybatis-spring-boot-starter&lt;/artifactId&gt;
&lt;version&gt;3.0.2&lt;/version&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-devtools&lt;/artifactId&gt;
&lt;scope&gt;runtime&lt;/scope&gt;
&lt;optional&gt;true&lt;/optional&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-docker-compose&lt;/artifactId&gt;
&lt;scope&gt;runtime&lt;/scope&gt;
&lt;optional&gt;true&lt;/optional&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
&lt;artifactId&gt;lombok&lt;/artifactId&gt;
&lt;optional&gt;true&lt;/optional&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-starter-test&lt;/artifactId&gt;
&lt;scope&gt;test&lt;/scope&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.mybatis.spring.boot&lt;/groupId&gt;
&lt;artifactId&gt;mybatis-spring-boot-starter-test&lt;/artifactId&gt;
&lt;version&gt;3.0.2&lt;/version&gt;
&lt;scope&gt;test&lt;/scope&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.jetbrains&lt;/groupId&gt;
&lt;artifactId&gt;annotations&lt;/artifactId&gt;
&lt;version&gt;RELEASE&lt;/version&gt;
&lt;scope&gt;compile&lt;/scope&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;jakarta.annotation&lt;/groupId&gt;
&lt;artifactId&gt;jakarta.annotation-api&lt;/artifactId&gt;
&lt;version&gt;1.3.5&lt;/version&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;org.junit.jupiter&lt;/groupId&gt;
&lt;artifactId&gt;junit-jupiter-api&lt;/artifactId&gt;
&lt;version&gt;5.9.3&lt;/version&gt;
&lt;scope&gt;test&lt;/scope&gt;
&lt;/dependency&gt;
&lt;dependency&gt;
&lt;groupId&gt;junit&lt;/groupId&gt;
&lt;artifactId&gt;junit&lt;/artifactId&gt;
&lt;version&gt;4.13.2&lt;/version&gt;
&lt;scope&gt;test&lt;/scope&gt;
&lt;/dependency&gt;
&lt;/dependencies&gt;
&lt;build&gt;
&lt;plugins&gt;
&lt;plugin&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-maven-plugin&lt;/artifactId&gt;
&lt;configuration&gt;
&lt;excludes&gt;
&lt;exclude&gt;
&lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
&lt;artifactId&gt;lombok&lt;/artifactId&gt;
&lt;/exclude&gt;
&lt;/excludes&gt;
&lt;/configuration&gt;
&lt;/plugin&gt;
&lt;/plugins&gt;
&lt;/build&gt;

</project>

Main

package com.example.demo.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@ComponentScan(basePackages = &quot;com.example.demo&quot;) // Add the package of your component
public class DemoApplication {
public static void main(String[] args) {
System.out.println(&quot;Demo&quot;);
SpringApplication.run(DemoApplication.class, args);
}
}

Spring Boot生成的项目打印两次。

Spring Boot生成的项目打印两次。

I have the demo code by this but I'm wondering why I get print twice.
I don't understand why this is happening.
I tried creating a different class but that class is not being called so tried this way.

答案1

得分: 1

如果您删除以下部分:

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

那么 System.out.println("Demo"); 将只打印一次,这是因为:

使用 spring-boot-devtools 的应用程序将在类路径上的文件更改时自动重新启动。在使用集成开发环境(IDE)时,这可以是一个有用的功能,因为它可以快速反馈代码更改。默认情况下,类路径上指向文件夹的任何条目都将被监视以进行更改。

简而言之:
开发工具会自动刷新上下文,而不需要手动重启。

英文:

If you`ll remove the

`&lt;dependency&gt;
&lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
&lt;artifactId&gt;spring-boot-devtools&lt;/artifactId&gt;
&lt;/dependency&gt;`

the System.out.println(&quot;Demo&quot;); will be printed just once, it happen because:

Applications that use spring-boot-devtools will automatically restart whenever files on the classpath change. This can be a useful feature when working in an IDE as it gives a very fast feedback loop for code changes. By default, any entry on the classpath that points to a folder will be monitored for changes.

In two words:
The devtools auto-refresh the context instead of restarting manually.

huangapple
  • 本文由 发表于 2023年8月10日 16:36:35
  • 转载请务必保留本文链接:https://go.coder-hub.com/76873975.html
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