spring(2)

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简介: spring

spring(1)https://developer.aliyun.com/article/1530428

2.2.9、实验九:p命名空间

引入p命名空间后,可以通过以下方式为bean的各个属性赋值

<bean id="studentSix" class="com.atguigu.spring.pojo.Student"
      p:id="1006" p:name="小明" p:clazz-ref="clazzOne" p:teacherMap-ref="teacherMap"></bean>

2.2.10、实验十:引入外部属性文件

①加入依赖
<!-- MySQL驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.16</version>
</dependency>
<!-- 数据源 -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.0.31</version>
</dependency>
②创建外部属性文件

jdbc.user=root
jdbc.password=atguigu
jdbc.url=jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC
jdbc.driver=com.mysql.cj.jdbc.Driver
③引入属性文件

[!note]

<!-- 引入外部属性文件 -->
<context:property-placeholder location="classpath:jdbc.properties"/>
④配置bean
<bean id="druidDataSource" class="com.alibaba.druid.pool.DruidDataSource">
    <property name="url" value="${jdbc.url}"/>
    <property name="driverClassName" value="${jdbc.driver}"/>
    <property name="username" value="${jdbc.user}"/>
    <property name="password" value="${jdbc.password}"/>
</bean>
⑤测试
@Test
public void testDataSource() throws SQLException {
    ApplicationContext ac = new ClassPathXmlApplicationContext("spring-datasource.xml");
    DataSource dataSource = ac.getBean(DataSource.class);
    Connection connection = dataSource.getConnection();
    System.out.println(connection);
}

2.2.11、实验十一:bean的作用域

①概念

在Spring中可以通过配置bean标签的scope属性来指定bean的作用域范围,各取值含义参加下表:

[!note]

scope:设置bean的作用域

scope=“singleton / prototype”

singleton(单例):表示获取该bean所对应的对象都是同一个

protcype(多例):表示获取该bean所对应的对象都不是同一个

取值 含义 创建对象的时机
singleton(默认) 在IOC容器中,这个bean的对象始终为单实例 IOC容器初始化时
prototype 这个bean在IOC容器中有多个实例 获取bean时
单例的情况有可能会出问题

11:10

  1. action是被ioc管理了,所以数据都是同一个
    但是通过网页上传的修改对象的功能已经修改的bean中的user类对象,user类对象中已经有id了,所以他使用的就是上一次的id,然后把后面添加的数据覆盖了第一次修改的数据

如果是在WebApplicationContext环境下还会有另外两个作用域(但不常用):

取值 含义
request 在一个请求范围内有效
session 在一个会话范围内有效

2.2.12、实验十二:bean的生命周期

①具体的生命周期过程
  • bean对象创建(调用无参构造器)
  • 给bean对象设置属性
  • bean对象初始化之前操作(由bean的后置处理器负责)
  • bean对象初始化(需在配置bean时指定初始化方法)
  • bean对象初始化之后操作(由bean的后置处理器负责)
  • bean对象就绪可以使用
  • bean对象销毁(需在配置bean时指定销毁方法)
  • IOC容器关闭
②修改类User
public class User {
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    public User() {
        System.out.println("生命周期:1、创建对象");
    }
    public User(Integer id, String username, String password, Integer age) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        System.out.println("生命周期:2、依赖注入");
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public void initMethod(){
        System.out.println("生命周期:3、初始化");
    }
    public void destroyMethod(){
        System.out.println("生命周期:5、销毁");
    }
    @Override
    public String toString() {
        return "User{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", password='" + password + '\'' +
            ", age=" + age +
            '}';
    }
}

注意其中的initMethod()和destroyMethod(),可以通过配置bean指定为初始化和销毁的方法

③配置bean

[!note]

使用init-method属性指定初始化方法

使用destroy-method属性指定销毁方法

<!-- 使用init-method属性指定初始化方法 -->
<!-- 使用destroy-method属性指定销毁方法 -->
<bean class="com.atguigu.bean.User" scope="prototype" init-method="initMethod"destroy-method="destroyMethod">
    <property name="id" value="1001"></property>
    <property name="username" value="admin"></property>
    <property name="password" value="123456"></property>
    <property name="age" value="23"></property>
</bean>
④测试

[!note]

1,实例化

2、依赖注入

3,初始化

4、IOC容器关时销毁

,

ConfiqurableApplicationContext是ApplicationContext的子接口,其中扩展了刷新和关闭容器的方法

@Test
public void testLife(){
    ConfiqurableApplicationContext ac = newClassPathXmlApplicationContext("spring-lifecycle.xml");
    User bean = ac.getBean(User.class);
    System.out.println("生命周期:4、通过IOC容器获取bean并使用");
    ac.close();
}

单例的时候在获取容器的时候就把对象给创建好,多例的时候是在获取bean的时候创建

⑤bean的后置处理器

bean的后置处理器会在生命周期的初始化前后添加额外的操作,需要实现BeanPostProcessor接口,

且配置到IOC容器中,需要注意的是,bean后置处理器不是单独针对某一个bean生效,而是针对IOC容器中所有bean都会执行

创建bean的后置处理器:

package com.atguigu.spring.process;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
public class MyBeanProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
        throws BeansException {
        System.out.println("☆☆☆" + beanName + " = " + bean);
        return bean;
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName)
        throws BeansException {
        System.out.println("★★★" + beanName + " = " + bean);
        return bean;
    }
}

在IOC容器中配置后置处理器:

<bean id="myBeanProcessor"class="com.atguigu.spring.process.MyBeanProcessor"/>

2.2.13、实验十三:FactoryBean

配置到ioc容器,获取的时候可以直接获取这个工厂提供的对象,不用先获取工厂再获取对象

①简介

FactoryBean是Spring提供的一种整合第三方框架的常用机制。和普通的bean不同,配置一个

FactoryBean类型的bean,在获取bean的时候得到的并不是class属性中配置的这个类的对象,而是

getObject()方法的返回值。通过这种机制,Spring可以帮我们把复杂组件创建的详细过程和繁琐细节都屏蔽起来,只把最简洁的使用界面展示给我们。

当把FactoryBean的实现类醒置为bean时,会将当前类中getobject()所返回的对象交给Ioc容器管理

将来我们整合Mybatis时,Spring就是通过FactoryBean机制来帮我们创建SqlSessionFactory对象的。

/*
* Copyright 2002-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.beans.factory;
import org.springframework.lang.Nullable;
/**
* Interface to be implemented by objects used within a {@link BeanFactory}
which
* are themselves factories for individual objects. If a bean implements this
* interface, it is used as a factory for an object to expose, not directly as a
* bean instance that will be exposed itself.
*
* <p><b>NB: A bean that implements this interface cannot be used as a normal
bean.</b>
* A FactoryBean is defined in a bean style, but the object exposed for bean
* references ({@link #getObject()}) is always the object that it creates.
*
* <p>FactoryBeans can support singletons and prototypes, and can either create
* objects lazily on demand or eagerly on startup. The {@link SmartFactoryBean}
* interface allows for exposing more fine-grained behavioral metadata.
*
* <p>This interface is heavily used within the framework itself, for example
for
* the AOP {@link org.springframework.aop.framework.ProxyFactoryBean} or the
* {@link org.springframework.jndi.JndiObjectFactoryBean}. It can be used for
* custom components as well; however, this is only common for infrastructure
code.
*
* <p><b>{@code FactoryBean} is a programmatic contract. Implementations are not
* supposed to rely on annotation-driven injection or other reflective
facilities.</b>
* {@link #getObjectType()} {@link #getObject()} invocations may arrive early in
the
* bootstrap process, even ahead of any post-processor setup. If you need access
to
* other beans, implement {@link BeanFactoryAware} and obtain them
programmatically.
*
* <p><b>The container is only responsible for managing the lifecycle of the
FactoryBean
* instance, not the lifecycle of the objects created by the FactoryBean.</b>
Therefore,
* a destroy method on an exposed bean object (such as {@link
java.io.Closeable#close()}
* will <i>not</i> be called automatically. Instead, a FactoryBean should
implement
* {@link DisposableBean} and delegate any such close call to the underlying
object.
*
* <p>Finally, FactoryBean objects participate in the containing BeanFactory's
* synchronization of bean creation. There is usually no need for internal
* synchronization other than for purposes of lazy initialization within the
* FactoryBean itself (or the like).
*
* @author Rod Johnson
* @author Juergen Hoeller
* @since 08.03.2003
* @param <T> the bean type
* @see org.springframework.beans.factory.BeanFactory
* @see org.springframework.aop.framework.ProxyFactoryBean
* @see org.springframework.jndi.JndiObjectFactoryBean
*/
public interface FactoryBean<T> {
    /**
* The name of an attribute that can be
* {@link org.springframework.core.AttributeAccessor#setAttribute set} on a
* {@link org.springframework.beans.factory.config.BeanDefinition} so that
* factory beans can signal their object type when it can't be deduced from
* the factory bean class.
* @since 5.2
*/
    String OBJECT_TYPE_ATTRIBUTE = "factoryBeanObjectType";
    /**
* Return an instance (possibly shared or independent) of the object
* managed by this factory.
* <p>As with a {@link BeanFactory}, this allows support for both the
* Singleton and Prototype design pattern.
* <p>If this FactoryBean is not fully initialized yet at the time of
* the call (for example because it is involved in a circular reference),
* throw a corresponding {@link FactoryBeanNotInitializedException}.
* <p>As of Spring 2.0, FactoryBeans are allowed to return {@code null}
* objects. The factory will consider this as normal value to be used; it
* will not throw a FactoryBeanNotInitializedException in this case anymore.
* FactoryBean implementations are encouraged to throw
* FactoryBeanNotInitializedException themselves now, as appropriate.
* @return an instance of the bean (can be {@code null})
* @throws Exception in case of creation errors
* @see FactoryBeanNotInitializedException
*/
    @Nullable
    T getObject() throws Exception;
    /**
* Return the type of object that this FactoryBean creates,
* or {@code null} if not known in advance.
* <p>This allows one to check for specific types of beans without
* instantiating objects, for example on autowiring.
* <p>In the case of implementations that are creating a singleton object,
* this method should try to avoid singleton creation as far as possible;
* it should rather estimate the type in advance.
* For prototypes, returning a meaningful type here is advisable too.
* <p>This method can be called <i>before</i> this FactoryBean has
* been fully initialized. It must not rely on state created during
* initialization; of course, it can still use such state if available.
* <p><b>NOTE:</b> Autowiring will simply ignore FactoryBeans that return
* {@code null} here. Therefore it is highly recommended to implement
* this method properly, using the current state of the FactoryBean.
* @return the type of object that this FactoryBean creates,
* or {@code null} if not known at the time of the call
* @see ListableBeanFactory#getBeansOfType
*/
    @Nullable
    Class<?> getObjectType();
    /**
* Is the object managed by this factory a singleton? That is,
* will {@link #getObject()} always return the same object
* (a reference that can be cached)?
* <p><b>NOTE:</b> If a FactoryBean indicates to hold a singleton object,
* the object returned from {@code getObject()} might get cached
* by the owning BeanFactory. Hence, do not return {@code true}
* unless the FactoryBean always exposes the same reference.
* <p>The singleton status of the FactoryBean itself will generally
* be provided by the owning BeanFactory; usually, it has to be
* defined as singleton there.
* <p><b>NOTE:</b> This method returning {@code false} does not
* necessarily indicate that returned objects are independent instances.
* An implementation of the extended {@link SmartFactoryBean} interface
* may explicitly indicate independent instances through its
* {@link SmartFactoryBean#isPrototype()} method. Plain {@link FactoryBean}
* implementations which do not implement this extended interface are
* simply assumed to always return independent instances if the
* {@code isSingleton()} implementation returns {@code false}.
* <p>The default implementation returns {@code true}, since a
* {@code FactoryBean} typically manages a singleton instance.
* @return whether the exposed object is a singleton
* @see #getObject()
* @see SmartFactoryBean#isPrototype()
*/
    default boolean isSingleton() {
        return true;
    }
}
②创建类UserFactoryBean
public class UserFactoryBean implements FactoryBean<User> {
    @Override
    public User getObject() throws Exception {
        return new User();
    }
    @Override
    public Class<?> getObjectType() {
        return User.class;
    }
}
③配置bean
<bean id="user" class="com.atguigu.bean.UserFactoryBean"></bean>
④测试
@Test
public void testUserFactoryBean(){
    //获取IOC容器
    ApplicationContext ac = new ClassPathXmlApplicationContext("spring-factorybean.xml");
    User user = (User) ac.getBean("user");
    System.out.println(user);
}

2.2.14、实验十基于xml的自动装配

自动装配:

根据指定的策略,在IOC容器中匹配某一个bean,自动为指定的bean中所依赖的类类型或接口类型属性赋值

ioc容器中所有类类型的属性,都可以在ioc容器中找到匹配的bean为属性赋值,之前是配置proprieties引用

①场景模拟

创建类UserController

public class UserController {
    private UserService userService;
    public void setUserService(UserService userService) {
        this.userService = userService;
    }
    public void saveUser(){
        userService.saveUser();
    }
}

创建接口UserService

public interface UserService {
  void saveUser();
}

创建类UserServiceImpl实现接口UserService

public class UserServiceImpl implements UserService {
    private UserDao userDao;
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
    @Override
    public void saveUser() {
        userDao.saveUser();
    }
}

创建接口UserDao

public interface UserDao {
  void saveUser();
}

创建类UserDaoImpl实现接口UserDao

public class UserDaoImpl implements UserDao {
    @Override
    public void saveUser() {
        System.out.println("保存成功");
    }
}

bean引用

[!danger]

引用的bean的实现类,当使用的实现类发生改变,换个新的实现类引用即可

<?xml version="1.0" encoding="UTF-8"?>  
<beans xmlns="http://www.springframework.org/schema/beans"  
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">  
<bean id="userController" class="com.atguigu.spring.controller.UserController">  
    <property name="userService" ref="userService"></property>  
</bean>  
  
  
    <bean id="userService" class="com.atguigu.spring.service.impl.UserServiceImpl">  
        <property name="userDao" ref="userDao"></property>  
    </bean>  
    <bean id="userDao" class="com.atguigu.spring.dao.imlp.UserDaoImpl"></bean>  
</beans>

测试

public class AutoWireTest {  
    @Test  
    public void testAutoWire(){  
        ApplicationContext ioc= new ClassPathXmlApplicationContext("spring-autowire.xml");  
        UserController bean = ioc.getBean(UserController.class);  
        bean.saveUser();  
    }  
}

②配置bean

使用bean标签的autowire属性设置自动装配效果

自动装配方式:byType

byType:根据类型匹配IOC容器中的某个兼容类型的bean,为属性自动赋值

若在IOC中,没有任何一个兼容类型的bean能够为属性赋值,则该属性不装配,即值为默认值

null

若在IOC中,有多个兼容类型的bean能够为属性赋值,则抛出异常

NoUniqueBeanDefinitionException

[!note]

总结:当使用byType实现自动装配时,IoC容器中有且只有一个类型匹配的bean能够为属性赋值,

而且相同类型的bean只需配一次,如果需要多个只需要设置作用域使之成为多例模式即可

<bean id="userController"class="com.atguigu.autowire.xml.controller.UserController" autowire="byType">
</bean>
<bean id="userService"class="com.atguigu.autowire.xml.service.impl.UserServiceImpl" autowire="byType">
</bean>
<bean id="userDao" class="com.atguigu.autowire.xml.dao.impl.UserDaoImpl"></bean>

自动装配方式:byName

byName:将自动装配的属性的属性名,作为bean的id在IOC容器中匹配相对应的bean进行赋值

<bean id="userController"class="com.atguigu.autowire.xml.controller.UserController" autowire="byName">
</bean>
<bean id="userService"class="com.atguigu.autowire.xml.service.impl.UserServiceImpl" autowire="byName">
</bean>
<bean id="userServiceImpl"class="com.atguigu.autowire.xml.service.impl.UserServiceImpl" autowire="byName">
</bean>
<bean id="userDao" class="com.atguigu.autowire.xml.dao.impl.UserDaoImpl">
</bean>
<bean id="userDaoImpl" class="com.atguigu.autowire.xml.dao.impl.UserDaoImpl">
</bean>

spring(3)https://developer.aliyun.com/article/1530433

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    JS字符串数据类型转换,字符串如何转成变量,+号只要有一个是字符串,就会把另外一个转成字符串,- * / 都会把数据转成数字类型,数字型控制台是蓝色,字符型控制台是黑色,
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  • 9
    JS数组操作---删除,arr.pop()方法从数组中删除最后一个元素,并返回该元素的值,arr.shift() 删除第一个值,arr.splice()方法,删除指定元素,arr.splice,从第一
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  • 10
    定义好变量,${age}模版字符串,对象可以放null,检验数据类型console.log(typeof str)
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