两种方式初始化：
1、配置文件 init-method

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http:///schema/beans"
       xmlns:xsi="http:///2001/XMLSchema-instance"
       xsi:schemaLocation="http:///schema/beans http:///schema/beans/spring-beans.xsd">


    <bean id="roleService" class=".service.RoleService" init-method="init"/>
</beans>

 */
public class RoleService {

    public RoleService() {
        System.out.println("RoleService 构造方法被初始化了....");
    }

    public void test(){
        System.out.println("RoleService test()....");
    }

    public void init(){
        System.out.println("RoleService init().....");
    }
}

运行结果

RoleService 构造方法被初始化了....
RoleService init().....
RoleService test()....
Disconnected from the target VM, address: '127.0.0.1:53138', transport: 'socket'

Process finished with exit code 0

2、实现接口 InitializingBean

@Service
public class RoleService implements InitializingBean {

    public RoleService() {
        System.out.println("RoleService 构造方法被初始化了....");
    }

    public void test(){
        System.out.println("RoleService test()....");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("RoleService afterPropertiesSet().....");
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http:///schema/beans"
       xmlns:xsi="http:///2001/XMLSchema-instance"
       xmlns:context="http:///schema/context"
       xsi:schemaLocation="http:///schema/beans http:///schema/beans/spring-beans.xsd http:///schema/context https:///schema/context/spring-context.xsd">

    <context:component-scan base-package=""/>
</beans>

运行结果

RoleService 构造方法被初始化了....
RoleService test()....
Disconnected from the target VM, address: '127.0.0.1:53158', transport: 'socket'

Process finished with exit code 0