Bean管理（2）

2021-01-29 分类 Spring 作者 Nayuki ~4.03K 字

FactoryBean

定义的bean类型和返回类型不一样
bean.xml

1	<bean id="musics" class="bean.Musics"></bean>

创建Musics类

public class Musics implements FactoryBean<Music>{
    @Override
    public Music getObject() throws Exception {
        Music music=new Music();
        music.setName("云烟成雨");
        return music;
    }
}

测试

1 2	Music music =context.getBean("musics", Music.class); System.out.println(music.getName());

Bean作用域

singleton：单实例
prototype：多实例
bean.xml

1	<bean id="music" class="bean.Music" scope="prototype"></bean>

测试

Music music1 =context.getBean("music", Music.class);
Music music2 =context.getBean("music", Music.class);
System.out.println(music1);
System.out.println(music2);

Bean生命周期

构造器创建实例
设置属性和引用其他bean
把实例传递 bean 后置处理器的方法 postProcessBeforeInitialization
调用初始化方法
把实例传递 bean 后置处理器的方法 postProcessAfterInitialization
对象获取
销毁实例

创建后置处理器类

public class MyBeanPost implements BeanPostProcessor {//创建后置处理器实现类
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("在初始化之前执行的方法");
        return bean;
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("在初始化之后执行的方法");
        return bean;
    }
}

bean.xml

<bean id="music" class="bean.Music" init-method="initMethod" destroy-method="destroyMethod">
    <property name="name" value="云烟成雨"></property>
</bean>
<bean id="myBeanPost" class="bean.MyBeanPost"></bean>

测试

1
2
3

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
Music music = context.getBean("music", music.class);
context.close();

XML自动装配

byName：根据名字自动装配
byType：根据类型自动装配
bean.xml

1 2	<bean id="student" class="bean.Student"autowire="byName"></bean> <bean id="course" class="bean.Course"></bean>

创建student类

public class Student {
   Course course;
    public Course getCourse() {
        return course;
    }
    public void setCourse(Course course) {
        this.course = course;
    }
}

外部属性文件

直接配置数据库信息

引入Druid连接池依赖jar包
配置Druid连接池

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
<property name="url" value="jdbc:mysql://localhost:3306/userDb"></property>
<property name="username" value="root"></property>
<property name="password" value="root"></property>
</bean>

引入外部属性文件配置数据库连接池

创建properties文件
引入context空间名：xmlns:context=”http://www.springframework.org/schema/context" xsi:schemaLocation=”http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"

prop.driverClass=com.mysql.jdbc.Driver
prop.url=jdbc:mysql://localhost:3306/userDb
prop.userName=root
prop.password=root

bean.xml

<context:property-placeholder location="classpath:jdbc.properties"/>

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
    <property name="driverClassName" value="${prop.driverClass}"></property>
    <property name="url" value="${prop.url}"></property>
    <property name="username" value="${prop.userName}"></property>
    <property name="password" value="${prop.password}"></property>
</bean>