文章目录

IOC-(DI)控制反转-(依赖注入)步骤1.set方法注入2.(有参)构造方法注入3.自动装配

IOC-(DI)控制反转-(依赖注入)步骤

IOC称之为控制反转，简单来说就是将对象 的创建的权力及对象的生命周期的管理过程交由Spring框架来处理，从此在开发过程中不在需要关注对象的创建和生命周期的管理,而是在需要的时候由Spring框架提供，这个由Spring框架管理对象创建和生命周期的机制称之为控制反转。而在创建对象的过程中Spring可以依据配置对象的属性进行设置，这个过程称之为依赖注入，也即DI

1.set方法注入

a. Spring内置可直接注入的类型

package cn.tedu.beans; import java.util.List; import java.util.Map; import java.util.Properties; import java.util.Set; public class Hero { private int id; private String name; private List<String> jobs; private Set<String> set; private Map<String,String> map; private Properties prop; private Dog dog; private Cat cat; public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setJobs(List<String> jobs) { this.jobs = jobs; } public void setSet(Set<String> set) { this.set = set; } public void setMap(Map<String, String> map) { this.map = map; } public void setProp(Properties prop) { this.prop = prop; } public void setDog(Dog dog) { this.dog = dog; } public void setCat(Cat cat) { this.cat = cat; } @Override public String toString() { return "Hero [id=" + id + ", name=" + name + ", jobs=" + jobs + ", set=" + set + ", map=" + map + ", prop=" + prop + ", dog=" + dog + ", cat=" + cat + "]"; } } <?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/springbeans3.2.xsd"> <bean id="hero" class="cn.tedu.beans.Hero"> <property name="id" value="123"></property> <property name="name" value="漂移崽"></property> <property name="jobs"> <list> <value>钢铁侠</value> <value>猪猪侠</value> <value>绿箭侠</value> <value>凹凸曼</value> </list> </property> <property name="set"> <set> <value>aaa</value> <value>bbb</value> <value>ccc</value> <value>aaa</value> </set> </property> <property name="map"> <map> <entry key="addr" value="王者荣耀"></entry> <entry key="addr" value="英雄联盟"></entry> <entry key="skill" value="风火轮"></entry> <entry key="age" value="19"></entry> </map> </property> <property name="prop"> <props> <prop key="kOne">v1</prop> <prop key="kTwo">v2</prop> <prop key="kThree">v3</prop> <prop key="kFour">v4</prop> </props> </property> </bean> </beans> /** * SpringDI set方式属性注入 - Spring内置的可直接注入类型的注入 */ @Test public void test1(){ ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); Hero hero = (Hero) context.getBean("hero"); System.out.println(hero); }

b. 非Spring内置可直接注入的类型

package cn.tedu.beans; import java.util.List; import java.util.Map; import java.util.Properties; import java.util.Set; public class Hero { private int id; private String name; private List<String> jobs; private Set<String> set; private Map<String,String> map; private Properties prop; private Dog dog; private Cat cat; public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setJobs(List<String> jobs) { this.jobs = jobs; } public void setSet(Set<String> set) { this.set = set; } public void setMap(Map<String, String> map) { this.map = map; } public void setProp(Properties prop) { this.prop = prop; } public void setDog(Dog dog) { this.dog = dog; } public void setCat(Cat cat) { this.cat = cat; } @Override public String toString() { return "Hero [id=" + id + ", name=" + name + ", jobs=" + jobs + ", set=" + set + ", map=" + map + ", prop=" + prop + ", dog=" + dog + ", cat=" + cat + "]"; } } <?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/springbeans3.2.xsd"> <bean id="hero" class="cn.tedu.beans.Hero"> <property name="id" value="123"></property> <property name="name" value="亚瑟 "></property> <property name="jobs"> <list> <value>钢铁侠</value> <value>猪猪侠</value> <value>绿箭侠</value> <value>凹凸曼</value> </list> </property> <property name="set"> <set> <value>aaa</value> <value>bbb</value> <value>ccc</value> <value>aaa</value> </set> </property> <property name="map"> <map> <entry key="addr" value="王者荣耀"></entry> <entry key="addr" value="英雄联盟"></entry> <entry key="skill" value="风火轮"></entry> <entry key="age" value="19"></entry> </map> </property> <property name="prop"> <props> <prop key="kOne">v1</prop> <prop key="kTwo">v2</prop> <prop key="kThree">v3</prop> <prop key="kFour">v4</prop> </props> </property> <property name="dog" ref="dog"></property> <property name="cat" ref="cat"></property> </bean> <bean id="dog" class="cn.tedu.beans.Dog"></bean> <bean id="cat" class="cn.tedu.beans.Cat"></bean> </beans>

/** * SpringDI set方式属性注入 - Spring内置的可直接注入类型的注入 */ @Test public void test2(){ ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); Hero hero = (Hero) context.getBean("hero"); System.out.println(hero); }

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2.(有参)构造方法注入

package cn.tedu.beans; public class Student { private int id; private String name; private Dog dog; public Student(int id, String name, Dog dog) { this.id = id; this.name = name; this.dog = dog; } @Override public String toString() { return "Student [id=" + id + ", name=" + name + ", dog=" + dog + "]"; } } <?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-3.2.xsd" > <bean id="student" class="cn.tedu.beans.Student"> <!-- index:为构造方法的第几个参数 进行配置,可以称为按下标来赋值(从0开始) name:为构造方法的哪个属性的参数进行配置 **index 和 name 可以配置任何一个或同时配置 但要求一旦配置必须正确 **推荐优先使用index方式配置 防止没有源码造成name无法匹配到对应参数 type:该构造方法参数的类型 value:该构造方法参数的值 ,用来指定基本值 ref:该构造方法参数的值,用来指定引用其他bean的值 --> <constructor-arg index="0" name="id" value="999"/> <constructor-arg index="1" type="java.lang.String" value="张无忌"/> <constructor-arg name="dog" ref="dog"/> </bean> <bean id="dog" class="cn.tedu.beans.Dog"></bean> </beans> /** * SpringDI 构造方法方式属性注入 */ @Test public void test3(){ ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); Student student = (Student) context.getBean("student"); System.out.println(student); }

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3.自动装配

在Spring的set方式实现的注入过程中，支持自动装配机制，所谓自动装配机制，会根据要设置的javabean属性的名字 或 类型 到spring中自动寻找对应id 或 类型的进行设置，从而 省去依次配置的过程，简化了配置。

a. 指定开始自动装配

<?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/springbeans3.2.xsd"> <!-- autowire设定自动装配： byName:根据javabean中需要注入的属性的名字 ，在spring容器中找对应id的<bean>将该<bean>的对象复制给 当前的属性 byType:根据javabean中需要注入的属性的类型，在spring容器中找对应class类型的<bean>将该<bean>的对象复制给 当前的属性 **byType方式 根据类型进行匹配，可能匹配到多个<bean>,此时会抛出异常。而byName是通过id来寻找<bean>，id没有重复，不会有这方面的问题，所以推荐使用byName方式 --> <bean id="teacher" class="cn.tedu.beans.Teacher" autowire="byName"></bean> <bean id="dog" class="cn.tedu.beans.Dog"></bean> <bean id="cat" class="cn.tedu.beans.Cat"></bean> </beans>

b. 全局配置自动装配

<?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/springbeans3.2.xsd"default-autowire="byName"> <!-- autowire设定自动装配： byName:根据javabean中需要注入的属性的名字 ，在spring容器中找对应id的<bean>将该<bean>的对象复制给 当前的属性 byType:根据javabean中需要注入的属性的类型，在spring容器中找对应class类型的<bean>将该<bean>的对象复制给 当前的属性 **byType方式 根据类型进行匹配，可能匹配到多个<bean>,此时会抛出异常。而byName是通过id来寻找<bean>，id没有重复，不会有这方面的问题，所以推荐使用byName方式 --> <bean id="teacher" class="cn.tedu.beans.Teacher"></bean> <bean id="dog" class="cn.tedu.beans.Dog"></bean> <bean id="cat" class="cn.tedu.beans.Cat"></bean> </beans> package cn.tedu.beans; public class Teacher { private Dog dog; private Cat cat; public void setDog(Dog dog) { this.dog = dog; } public void setCat(Cat cat) { this.cat = cat; } @Override public String toString() { return "Teacher [dog=" + dog + ", cat=" + cat + "]"; } } /** * SpringDI 自动装配 */ @Test public void test4(){ ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); Teacher teacher = (Teacher) context.getBean("teacher"); System.out.println(teacher); }