作用
@Configuration注解在类上，将该类设置为springboot的配置类，相当于springmvc中的xml文件。
配置类本身也是一个组件和容器。
被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被扫描，并用于构建bean定义，初始化Spring容器。
proxyBeanMethods ： 存在组件依赖时，属性值应该为true，不存在组件依赖时，可以用false。
编码实现
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>org.example</groupId>
<artifactId>springboot-learning</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.3.7.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.session</groupId>
<artifactId>spring-session-core</artifactId>
</dependency>
<!-- <dependency>-->
<!-- <groupId>org.mybatis.spring.boot</groupId>-->
<!-- <artifactId>mybatis-spring-boot-starter</artifactId>-->
<!-- <version>2.1.3</version>-->
<!-- </dependency>-->
<!-- <dependency>-->
<!-- <groupId>mysql</groupId>-->
<!-- <artifactId>mysql-connector-java</artifactId>-->
<!-- <version>8.0.25</version>-->
<!-- <scope>runtime</scope>-->
<!-- </dependency>-->
<!-- <dependency>-->
<!-- <groupId>org.springframework.boot</groupId>-->
<!-- <artifactId>spring-boot-starter-test</artifactId>-->
<!-- <scope>test</scope>-->
<!-- </dependency>-->
<!-- <dependency>-->
<!-- <groupId>junit</groupId>-->
<!-- <artifactId>junit</artifactId>-->
<!-- <version>4.12</version>-->
<!-- <scope>test</scope>-->
<!-- </dependency>-->
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
将MyConfig.java设置为Springboot的配置类：
MyConfig.java
package com.zwy.boot.config;
import ch.qos.logback.core.db.DBHelper;
import com.zwy.boot.bean.Pet;
import com.zwy.boot.bean.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
/**
* 1.配置类里面使用@Bean标注在方法上，给容器注册组件，默认也是单实例的
* 2.配置类本身也是组件
* 3.proxyBeanMethods: 代理bean的方法
* Full(proxyBeanMethods = true) 默认，调用多次方法，只产生一个对象
* Lite(proxyBeanMethods = false) 每次调用这些方法，都会产生一个新的对象
* 给容器中自动创建出这两个类型的组件，组件名字默认是全类名
* @author zwy
*/
@Configuration(proxyBeanMethods = true)
public class MyConfig {
/**
* 外部无论对配置类中这个组件注册方法调用多少次，获取的都是之前注册容器中的单实例对象
* @return User
*/
@Bean
public User user01() {
User zhangsan = new User("zhangsan", 18);
// User组件依赖了Pet组件
zhangsan.setPet(tomcatPet());
return zhangsan;
}
@Bean
public Pet tomcatPet() {
return new Pet("tomcat");
}
}
其中启动类有： MainApplication.java
package com.zwy.boot;
import ch.qos.logback.core.db.DBHelper;
import com.zwy.boot.bean.Pet;
import com.zwy.boot.bean.User;
import com.zwy.boot.config.MyConfig;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
/**
* 主程序类; 主配置类
* 注解@SpringBootApplication：这是一个springboot应用
* @author zwy
*/
@SpringBootApplication
public class MainApplication {
public static void main(String[] args) {
// 1.返回IOC容器
ConfigurableApplicationContext run = SpringApplication.run(MainApplication.class, args);
// 2.查看容器里面的组件
String[] names = run.getBeanDefinitionNames();
for (String name : names) {
System.out.println(name);
}
System.out.println("======================");
// 3.从容器中获取组件，注册
Pet pet1 = run.getBean("tom", Pet.class);
Pet pet2 = run.getBean("tom", Pet.class);
System.out.println("组件：" + (pet1 == pet2));
MyConfig bean = run.getBean(MyConfig.class);
System.out.println(bean);
User user1 = bean.user01();
User user2 = bean.user01();
System.out.println(user1 == user2);
// 4.验证proxyBeanMethods=false时，用户的宠物是不是容器中的宠物？
User user01 = run.getBean("user01", User.class);
Pet tom = run.getBean("tom", Pet.class);
System.out.println("用户的宠物：" + (user01.getPet() == tom));
}
}
另外有：
User.java
package com.zwy.boot.bean;
/**
* 用户
* @author zwy
*/
public class User {
private String name;
private Integer age;
private Pet pet;
public User() {
}
public User(String name, Integer age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Pet getPet() {
return pet;
}
public void setPet(Pet pet) {
this.pet = pet;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
", pet=" + pet +
'}';
}
}
Pet.java
package com.zwy.boot.bean;
/**
* 宠物
* @author zwy
*/
public class Pet {
private String name;
public Pet() {
}
public Pet(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Pet{" +
"name='" + name + '\'' +
'}';
}
}
文件结构
有文件结构如下：
运行
如果proxyBeanMethods = false，每次调用这些方法，都会产生一个新的对象，此时用户的宠物就不是宠物了，会显示用户的宠物：false
