Deeper understanding of Spring Boot: bean management, principles of analysis and Maven advanced applications

preamble

Hello everyone, today we are going to talk about the core content of Spring Boot, including bean management, how Spring Boot works, and advanced applications of Maven. These contents are not only the foundation of Spring Boot, but also the problems we often encounter in the actual project. I hope that through this article, we can let you have a deeper understanding of Spring Boot.

I. Bean Management

1.1 What is a Bean?

In Spring, a bean is an object that is managed by the Spring IoC container. Simply put, a bean is an object that is instantiated, assembled, and managed by the Spring Framework.

1.2 Bean life cycle

The life cycle of a bean consists of the following stages:

instantiated: The Spring container creates bean instances through a reflection mechanism.
attribute assignment: The Spring container injects property values from the configuration file or from annotations into the bean.
initialization: If the bean implements theInitializingBeaninterface, which calls theafterPropertiesSet()method; if configuredinit-method, which will call the specified initialization method.
utilization: The bean is used by the application.
destroy (by melting or burning): If the bean implements theDisposableBeaninterface, which calls thedestroy()method; if configureddestroy-method, the specified destruction method will be called.

1.3 Scope of Bean

Spring provides a variety of bean scopes, the following are commonly used:

singleton: By default scoping, there is only one bean instance in the entire Spring IoC container.
prototype: A new instance of the bean is created for each request.
request: Each HTTP request creates a new instance of the bean for web applications.
session: Each HTTP session creates a new instance of the bean for web applications.

1.4 Code Examples

Below is a simple example of a bean definition and usage:

import ;
import ;

@Configuration
public class AppConfig {

    @Bean
    public MyBean myBean() {
        return new MyBean();
    }
}

public class MyBean {
    public void doSomething() {
        ("Doing something...");
    }
}

import ;
import ;

public class Main {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext();
        MyBean myBean = ();
        ();
    }
}

Second, the principle of Spring Boot

2.1 Automatic configuration

Spring Boot's auto-configuration is one of its core features. It does this through the@EnableAutoConfigurationannotation and a series ofAutoConfigurationclasses to enable autoconfiguration.Spring Boot automatically configures all aspects of a Spring application based on conditions such as dependencies in class paths, properties in configuration files, and so on.

2.2 Conditional annotations

Spring Boot uses a number of conditional annotations for autoconfiguration, for example:

@ConditionalOnClass: The configuration takes effect when the specified class exists in the class path.
@ConditionalOnMissingBean: The configuration takes effect when the specified bean does not exist in the Spring container.
@ConditionalOnProperty: The configuration takes effect when the specified attribute is present in the configuration file.

2.3 Code Examples

Below is a simple example of auto-configuration:

import ;
import ;
import ;

@Configuration
@ConditionalOnClass(name = "")
public class MyAutoConfiguration {

    @Bean
    public MyService myService() {
        return new MyService();
    }
}

public class MyService {
    public void serve() {
        ("Serving...");
    }
}

III. Maven Advanced Applications

3.1 Multi-module projects

In real projects, we often use Maven to manage multi-module projects. Multi-module projects can manage different functional modules separately to improve the maintainability and reusability of the code.

3.2 Dependency Management

Maven's dependency management is very powerful, and can be accessed through the<dependencyManagement>tag to unify the management of the project's dependent versions and avoid version conflicts.

3.3 Plug-in use

Maven provides a wealth of plug-ins that can be used to achieve a variety of build tasks , such as compiling , packaging , testing and so on.

3.4 Code Examples

Below is a simple example of a multi-module project:

<!-- fatherPOMfile -->
<project xmlns="/POM/4.0.0" xmlns:xsi="http:///2001/XMLSchema-instance"
         xsi:schemaLocation="/POM/4.0.0 /xsd/maven-4.0.">
    <modelVersion>4.0.0</modelVersion>
    <groupId></groupId>
    <artifactId>parent-project</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <modules>
        <module>module-a</module>
        <module>module-b</module>
    </modules>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId></groupId>
                <artifactId>spring-boot-starter</artifactId>
                <version>2.5.4</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

<!-- submoduleA(used form a nominal expression)POMfile -->
<project xmlns="/POM/4.0.0" xmlns:xsi="http:///2001/XMLSchema-instance"
         xsi:schemaLocation="/POM/4.0.0 /xsd/maven-4.0.">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId></groupId>
        <artifactId>parent-project</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <artifactId>module-a</artifactId>
</project>

<!-- submoduleB(used form a nominal expression)POMfile -->
<project xmlns="/POM/4.0.0" xmlns:xsi="http:///2001/XMLSchema-instance"
         xsi:schemaLocation="/POM/4.0.0 /xsd/maven-4.0.">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId></groupId>
        <artifactId>parent-project</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <artifactId>module-b</artifactId>
</project>

summarize

Through this article, we delve into the Spring Boot bean management, the principle of work and the advanced application of Maven. I hope this content can help you better understand and use Spring Boot. if you have any questions or suggestions, welcome to leave a message in the comments section, we exchange learning together!

Thanks for reading and we'll see you next time!

The AI essay writing tool used by millions of college students with no duplicates 👉:.AI Writes Essays