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Spring IOC

2020-06-10 16:06:18来源：博客园阅读 ()

Spring IOC

1.SpringIOC的本质

Spring ioc指的是控制反转，IOC容器负责实例化、定位、配置应用程序中的对象及建立这些对象间的依赖。交由Spring容器统一进行管理，从而实现松耦合.（解耦）

控制反转（ioc）他是一种设计思想

来源于狂神说--------------------->狂神说java，见解很细，很到位，

个人这个图对ioc的解释很到位，容易理解

2.Spring 入门

1.创建一个Maven项目

这里我就不在细说了。参考我之前的博客环境搭建

2.配置依赖

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
        </dependency>
       <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-webmvc</artifactId>
           <version>5.2.5.RELEASE</version>
       </dependency>
       <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-jdbc</artifactId>
           <version>5.2.5.RELEASE</version>
       </dependency>

3.编写代码

1.准备测试的实体类

public class User {
private String username;
private String password;
}

2.配置spring的xml文件

命名applicationContext.xml

<?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-4.1.xsd">

   <!--bean就是一个java对象,由Spring创建和管理-->
   <bean id="user" class="com.lgw.pojo.User">
        <!--set注入-->
   <property name="username" value="root"/>
   <property name="password" value="123"/>  
        <!--构造器注入-->
<!--        <constructor-arg name="username" value="2"></constructor-arg>-->
<!--        <constructor-arg name="password" value="1"></constructor-arg>-->
   </bean>
</beans

bean相当于set方法创建对象

public void setUse(User user) {
      this.user = user;
}

依赖注入（Dependency Injection,DI）
- property 注入
- constructor-arg 注入

3.junit测试

  @Test
  public void IocTest2(){
      /*获取Spring配置文件*/
      ApplicationContext applicationContext= new ClassPathXmlApplicationContext("applicationContext.xml");
      /*1.反射获取*/
      User bean = applicationContext.getBean(User.class);
      /*2.bean--id获取*/
      User bean1 = (User) applicationContext.getBean("user");
      System.out.println(bean+"-----"+bean.hashCode());
      System.out.println(bean1+"-----"+bean1.hashCode());
  }

ClassPathXmlApplicationContext来获取applicationContext.xml配置文件
在使用getBean()来获取对象(1.反射获取，2 bean id获取)
getBean()默认创建对象为单例

3.DI注入

1.准备一个实体类

public class Student {
    private String name;
    private Address address;
    private String[] books;
    private List<String> hobbys;
    private Map<String,String> map;
    private Set<String> set;
    private String wife;
    private Properties info;
}

2.xml配置文件实现Dl注入

<?xml version="1.0" encoding="UTF-8"?>
<beans
        xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:p="http://www.springframework.org/schema/p"
        xmlns:c="http://www.springframework.org/schema/c"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
		http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<!--p标签   p:address="12"  property
c:address=""  构造器      -->
<bean class="com.lgw.pojo.Address" id="address" p:address="12" >
    
</bean>
<!--autowire自动装配  -->
 <bean class="com.lgw.pojo.Student" id="student"  >
<!-- 普通的set注入-->
     <property name="name" value="普通的set注入"/>
     <!--引用bean注入 ref-->
     <property name="address" ref="address"/>
      <!--数组-->
     <property name="books" >
         <array value-type="java.lang.String">
             <value>book1</value>
             <value>book2</value>
         </array>
     </property>
<!--list集合-->
     <property name="hobbys">
         <list>
             <value>hobby1</value>
             <value>hobby2</value>
         </list>
     </property>
<!-- map集合-->
     <property name="map" >
         <map>
             <entry key="map" value="Spring"/>
             <entry key="map1" value="SpringIOC"/>
         </map>
     </property>
     <!--  set集合-->
     <property name="set">
         <set>
             <value>COC</value>
         </set>
     </property>     
<!-- null-->
     <property name="wife">
         <null></null>
     </property>    
     <!--propreties-->
     <property name="info">
         <props>
             <prop key="name">root</prop>
         </props>
     </property>
 </bean>
</beans>

4.Spring的注解

1.xml配置注解的约束

<?xml version="1.0" encoding="UTF-8"?>
 <beans
         xmlns="http://www.springframework.org/schema/beans"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:p="http://www.springframework.org/schema/p"
         xmlns:context="http://www.springframework.org/schema/context"
         xsi:schemaLocation="http://www.springframework.org/schema/beans
 	    http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
 	    http://www.springframework.org/schema/context
 	    http://www.springframework.org/schema/context/spring-context.xsd">
    <!--开启注解--> 
<context:annotation-config/>
     <!-- com.*或者com..*都可以   扫描com包下面的 -->
     <context:component-scan base-package="com.*"></context:component-scan>
 </beans>

2.注解的使用

注解说明-

@Service用于Service层
@repository 用于dao层-
@controller用于action层
@component其他类

本质上没有区别。只是为了区分

@Component
@Scope(value = "singleton")
public class People {

    @Autowired
    @Qualifier(value = "knife")
	private arms a;
	private String name;
	@Override
	public String toString() {
		return "People{" +
				"a=" + a +
				", name='" + name + '\'' +
				'}';
	}
}

@Autowired(required = false) 通过byType寻找
@Qualifier(value="gun") //选择哪个Value值为对应的值
@Nullable 注解后,字段可以为null
@Scope 作用域
@value 赋值(简单赋值)

3.junit测试

    @Test
    public void  Test1(){
      ApplicationContext ApplicationContext = new         ClassPathXmlApplicationContext("applicationContext.xml");
        People bean = ApplicationContext.getBean(People.class);
        System.out.println(bean);
    }

运行结果：
People{a=knife{type='刀'}, name='null'}

注解开发先对于xml开发要方便快速的很多。

4.纯注解Spring

完全使用注解开发

1.java配置文件

@Configuration跟applicationContext.xml配置拥有同等效益

@bean相当于xml的bean标签

@Configuration
@ComponentScan("com.*")//扫描 默认扫描
public class appConfig {

    @Bean
    public User user(){
        return  new User();
    }

    @Bean
    public People people(){
        return new People();
    }
}