【Spring】(五)依赖注入

依赖注入

1.构造器注入

​ 【Spring】(三)IOC创建对象的方式

2.set方式注入【重点】

• 依赖注入：Set注入
  • 依赖：bean对象的创建依赖于容器
  • 注入：bean对象中的所有属性，由容器来注入

​ 【环境搭建】

• 1.Address

  public class Address {
      private String address;
      ...
  }
  

• 2.Student

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

• 3.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
          https://www.springframework.org/schema/beans/spring-beans.xsd">
  
      <bean id="address" class="pojo.Address">
          <property name="address" value="西安"></property>
      </bean>
  
      <bean id="student" class="pojo.Student">
          <!--普通注入，value-->
          <property name="name" value="兰"/>
  
          <!--Bean注入，ref-->
          <property name="address" ref="address"/>
  
          <!--数组-->
          <property name="books">
              <array>
                  <value>红楼梦</value>
                  <value>西游记</value>
                  <value>水浒传</value>
                  <value>三国演义</value>
              </array>
          </property>
  
          <!--list-->
          <property name="hobbys">
              <list>
                  <value>听歌</value>
                  <value>敲代码</value>
                  <value>看电影</value>
              </list>
          </property>
  
          <!--Map-->
          <property name="card">
              <map>
                  <entry key="身份证" value="111111111"/>
                  <entry key="银行卡" value="222222222"/>
              </map>
          </property>
  
          <!--Set-->
          <property name="games">
              <set>
                  <value>LOL</value>
                  <value>COC</value>
                  <value>BOB</value>
              </set>
          </property>
  
          <!--null-->
          <property name="wife">
              <null/>
          </property>
  
          <!--Properties-->
          <property name="info">
              <props>
                  <prop key="driver">20190525</prop>
                  <prop key="url">男</prop>
                  <prop key="username">root</prop>
                  <prop key="password">123</prop>
              </props>
          </property>
      </bean>
  
  </beans>
  

• 4.MyTest

  public class MyTest {
      public static void main(String[] args) {
          ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
          Student student = (Student) context.getBean("student");
          System.out.println(student.toString());
          
          //结果
          /*Student{
              name='兰',
              address=Address{address='西安'},
              books=[红楼梦, 西游记, 水浒传, 三国演义],
              hobbys=[听歌, 敲代码, 看电影],
              card={身份证=111111111, 银行卡=222222222},
              games=[LOL, COC, BOB],
              wife='null',
              info={password=123, url=男, driver=20190525, username=root}}
           */
      
      }
  } 
  

  
  

3.拓展方式注入

• User.java

  public class User {
      private String name;
      private String age;
  
      public User() {
      }
  
      public User(String name, String age) {
          this.name = name;
          this.age = age;
      }
      ...
  }
  

• userbean.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"
         xmlns:p="http://www.springframework.org/schema/p"
         xmlns:c="http://www.springframework.org/schema/c"
         xsi:schemaLocation="http://www.springframework.org/schema/beans
          https://www.springframework.org/schema/beans/spring-beans.xsd">
  
      <!--p命名空间注入，可以直接注入属性的值：property-->
      <bean id="user" class="pojo.User" p:name="蓝" p:age="18"></bean>
  
      <!--c命名空间注入，通过构造器注入：construct-args -->
      <bean id="user2" class="pojo.User" c:age="18" c:name="蓝紫"></bean>
      
  </beans>
  

• 测试类

  public void test2(){
          ApplicationContext context = new ClassPathXmlApplicationContext("userbean.xml");
          User user=context.getBean("user2",User.class);
          System.out.println(user);
  }
  

*注意：p命名和c命名空间不能直接使用，需要导入xml约束

xmlns:p="http://www.springframework.org/schema/p"
xmlns:c="http://www.springframework.org/schema/c"

4.bean的作用域

• 1.单例模式（Spring默认机制）一个实例只会被创建一次

  <bean id="user2" class="pojo.User" c:age="18" c:name="蓝紫" scope="singleton" />
  

  

  测试：一个实例只会被创建一次，所以取出来的对象是同一个

   public void test2(){
          ApplicationContext context = new ClassPathXmlApplicationContext("userbean.xml");
          User user=context.getBean("user2",User.class);
          User user2=context.getBean("user2",User.class);
  
          System.out.println(user==user2);//true
      }
  

• 2.原型模式：每次从容器中get时，都会产生一个新对象。

  <bean id="user2" class="pojo.User" c:age="18" c:name="蓝紫" scope="prototype" />
  

  

  测试

  System.out.println(user==user2);//false
  

• 3.其余的request、session、application，这些只能在web开发中使用到。