spring（一） IOC 控制反转、DI 依赖注入

IOC 控制反转：创建对象的方式变成了由Spring来主导

IOC底层原理：对象工厂

1、导入jar包：4个核心jar和1个依赖jar

spring-beans-4.3.9.RELEASE.jar

spring-context-4.3.9.RELEASE.jar

spring-core-4.3.9.RELEASE.jar

spring-expression-4.3.9.RELEASE.jar

com.springsource.org.apache.commons.logging-1.1.1.jar

2、添加xml配置文件：applicationContext.xml 约定俗成

 1 <?xml version="1.0" encoding="UTF-8"?>
 2     <beans xmlns="http://www.springframework.org/schema/beans"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="
 5     http://www.springframework.org/schema/beans  http://www.springframework.org/schema/beans/spring-beans.xsd">
 6         <bean id="foo" class="x.y.Foo">
 7             <meta key="cacheName" value="foo"/>
 8             <property name="name" value="Rick"/>
 9         </bean>
10   </beans>

3、在xml中beans标签里注册类

Class属性一定为全路径（因为ioc的底层实现是通过反射技术）

id：通过id来获取本类对象，一般为类名（首字母小写）

1  <bean id="studentId" class="com.spring.Student">
2  </bean>

4、获取对象方式

1     //初始化spring 容器
2     ApplicationContext con = new ClassPathXmlApplicationContext("applicationContext.xml");
3     //通过 getBean() 获取对象
4     Student stu = (Student)con.getBean("studentId");
5     stu.study();

scope

scope= "prototype"多实例。 scope= " singleton "单例

默认为单例模式 singleton

lazy-init

lazy-init = "true"；懒加载：使用时再创建对象

lazy-init = "false"；默认为false。容器初始化时创建对象

DI 依赖注入

概念：启动Spring容器加载bean配置的时候，完成对变量的赋值行为

一：使用xml表配置注入：

1、有参构造注入

1     public Student(String name, int age) {
2         super();
3         this.name = name;
4         this.age = age;
5     }

1     <bean id="studentId" class="com.spring.Student" scope="singleton" lazy-init="true">
2     
3         <constructor-arg name="name" value="刘杨哥哥"></constructor-arg>
4         <constructor-arg name="age" value="20"></constructor-arg>
5 
6     </bean>

2、Set方法注入

 1     public String getName() {
 2         return name;
 3     }
 4     public void setName(String name) {
 5         this.name = name;
 6     }
 7     
 8     public int getAge() {
 9         return age;
10     }
11     public void setAge(int age) {
12         this.age = age;
13     }

1    <bean id="studentId" class="com.spring.Student" scope="singleton" lazy-init="true">
2 
3         <property name="name" value="liuyang"></property>
4         <property name="age" value="20"></property>
5         
6    </bean>

3、属性为对象的注入方式

 1 package com.spring_ioc1;
 2 
 3 public class Clazz {
 4     
 5     private Student stu;
 6     
 7     public Student getStu() {
 8         return stu;
 9     }
10     public void setStu(Student stu) {
11         this.stu = stu;
12     }
13 
14     public void clzzbegin(){
15         
16 //        clazz依赖学生
17         
18         System.out.println("=== 开始上课  ===");
19         stu.study();
20     }
21     
22 }

1     <!-- 依赖注入: clazz依赖学生: 所以需注入学生 -->
2     <bean id="clazzId" class="com.spring.Clazz" scope="singleton" lazy-init="true">
3         <property name="stu" ref="studentId"></property>
4     </bean>

4、特殊类型的对象的注入

　　数组、List集合、Map集合

 1 package com.spring_ioc1;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Map;
 5 
 6 public class Property {
 7     
 8     private String arr[];
 9     private ArrayList<String> list;
10     private Map map;
11     
12     public String[] getArr() {
13         return arr;
14     }
15     public void setArr(String[] arr) {
16         this.arr = arr;
17     }
18     public ArrayList<String> getList() {
19         return list;
20     }
21     public void setList(ArrayList<String> list) {
22         this.list = list;
23     }
24     public Map getMap() {
25         return map;
26     }
27     public void setMap(Map map) {
28         this.map = map;
29     }
30     public Property() {
31         super();
32     }
33     
34 }

 1     <bean id="propertyId" class="com.spring.Property">
 2         <property name="arr">
 3             <list>
 4                 <value>arr刘杨</value>
 5                 <value>arr刘超</value>
 6                 <value>arr刘聪</value>
 7             </list>
 8         </property>
 9         <property name="list">
10             <list>
11                 <value>list刘杨</value>
12                 <value>list刘超</value>
13                 <value>list刘聪</value>
14             </list>
15         </property>
16         <property name="map">
17             <map>
18                 <entry key="1" value="map刘杨"></entry>
19                 <entry key="2" value="map刘超"></entry>
20                 <entry key="3" value="map刘聪"></entry>
21             </map>
22         </property>
23     </bean>

二：使用注解注入：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="
 5         http://www.springframework.org/schema/beans 
 6         http://www.springframework.org/schema/beans/spring-beans.xsd
 7         http://www.springframework.org/schema/context 
 8         http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->
 9     
10     <!-- 自动扫描 配置  扫描所有注解 :使用注解注入 -->
11     <context:component-scan base-package="com.spring_ioc2"></context:component-scan>
12     
13 </beans>

 1 package com.spring_ioc2;
 2 
 3 import javax.annotation.Resource;
 4 
 5 import org.springframework.beans.factory.annotation.Autowired;
 6 import org.springframework.beans.factory.annotation.Value;
 7 import org.springframework.context.annotation.Lazy;
 8 import org.springframework.context.annotation.Scope;
 9 import org.springframework.stereotype.Component;
10 
11 @Component(value="clazzId")    //相当于 <bean id="clazzId" class="com.spring.clazz"></bean>
12 //@Scope(value="prototype")
13 @Lazy
14 public class Clazz {
15     
16     @Value("gs02班") // <property name="" value="">
17     private String name;
18     
19     //@Autowired //根据student 的类型寻找        // <property name="" ref="">
20     @Resource(name="student") //指定别名扫描寻找
21     private Student stu;
22     
23     public String getName() {
24         return name;
25     }
26     public void setName(String name) {
27         this.name = name;
28     }
29     public Student getStu() {
30         return stu;
31     }
32     public void setStu(Student stu) {
33         this.stu = stu;
34     }
35     
36     
37     public Clazz(){
38         System.out.println("=== clazz初始化完成  ===");
39     }
40     
41     
42     public void clzzBegin(){
43         
44         System.out.println("=== 开始上课喽  ===");
45         //stu.study();
46     }
47     
48 }

 1 package com.spring_ioc2;
 2 
 3 import org.springframework.beans.factory.annotation.Value;
 4 import org.springframework.stereotype.Component;
 5 
 6 @Component("student")
 7 public class Student {
 8     
 9     @Value("刘杨")
10     private String name;
11     private int age;
12     
13 
14     public Student() {
15         System.out.println("=== student初始化完成  ===");
16     }
17     
18     public Student(String name) {
19         this.name = name;
20     }
21     
22 
23     public Student(String name, int age) {
24         super();
25         this.name = name;
26         this.age = age;
27     }
28 
29     public String getName() {
30         return name;
31     }
32     public void setName(String name) {
33         this.name = name;
34     }
35     
36     public int getAge() {
37         return age;
38     }
39     public void setAge(int age) {
40         this.age = age;
41     }
42     
43     
44     public void study(){
45         System.out.println("Student study  正在努力学习!!!");
46     }
47 }

三：xml表与注解混合使用注入

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="
 5         http://www.springframework.org/schema/beans 
 6         http://www.springframework.org/schema/beans/spring-beans.xsd
 7         http://www.springframework.org/schema/context 
 8         http://www.springframework.org/schema/context/spring-context.xsd"> <!-- bean definitions here -->
 9         
10     <!-- 自动扫描 配置  扫描有限注解   :xml表与注解混合使用注入-->
11     <context:annotation-config></context:annotation-config>
12     
13     <!--注册类 -->
14     <bean id="clazzId" class="com.spring_ioc3.Clazz"></bean>
15     <bean id="student" class="com.spring_ioc3.Student"></bean>
16     
17 </beans>

 1 package com.spring_ioc3;
 2 
 3 import javax.annotation.Resource;
 4 
 5 import org.springframework.beans.factory.annotation.Autowired;
 6 import org.springframework.beans.factory.annotation.Value;
 7 import org.springframework.context.annotation.Lazy;
 8 import org.springframework.context.annotation.Scope;
 9 import org.springframework.stereotype.Component;
10 
11 public class Clazz {
12     
13     @Value("gs02班") // <property name="" value="">
14     private String name;
15     
16     //@Autowired //根据student 的类型寻找        // <property name="" ref="">
17     @Resource(name="student") //指定别名扫描寻找
18     private Student stu;
19     
20     public String getName() {
21         return name;
22     }
23     public void setName(String name) {
24         this.name = name;
25     }
26     public Student getStu() {
27         return stu;
28     }
29     public void setStu(Student stu) {
30         this.stu = stu;
31     }
32     
33     
34     public Clazz(){
35         System.out.println("=== clazz初始化完成  ===");
36     }
37     
38     public void clzzBegin(){
39         
40         System.out.println("=== 开始上课喽  ===");
41         //stu.study();
42     }
43     
44 }

 1 package com.spring_ioc3;
 2 
 3 import org.springframework.beans.factory.annotation.Value;
 4 import org.springframework.stereotype.Component;
 5 
 6 
 7 public class Student {
 8     
 9     @Value("刘杨")
10     private String name;
11     private int age;
12     
13 
14     public Student() {
15         System.out.println("=== student初始化完成  ===");
16     }
17     
18     public Student(String name) {
19         this.name = name;
20     }
21     
22 
23     public Student(String name, int age) {
24         super();
25         this.name = name;
26         this.age = age;
27     }
28 
29     public String getName() {
30         return name;
31     }
32     public void setName(String name) {
33         this.name = name;
34     }
35     
36     public int getAge() {
37         return age;
38     }
39     public void setAge(int age) {
40         this.age = age;
41     }
42     
43     
44     public void study(){
45         System.out.println("Student study  正在努力学习!!!");
46     }
47 }

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原文地址：https://www.cnblogs.com/liuyangv/p/8508388.html

spring（一） IOC 控制反转 、DI 依赖注入

DI 依赖注入

spring（一） IOC 控制反转、DI 依赖注入