spring的三种注入方式：

1. 接口注入（不推荐）
2. getter，setter方式注入（比较常用）
3. 构造器注入（死的应用）

•  autowire="defualt"
•  autowire=“byName”
•  autowire="bytype"

例如：有如下两个类需要注入

package org.jia;
 2 
 3 public class Order {
 4     private String orderNum;
 5     @SuppressWarnings("unused")
 6     private OrderItem orderitem;
 7 
 8     public OrderItem getOrderitem() {
 9         return orderitem;
10     }
11 
12     public void setOrderitem(OrderItem orderitem) {
13         this.orderitem = orderitem;
14     }
15 
16     public String getOrderNum() {
17         return orderNum;
18     }
19 
20     public void setOrderNum(String orderNum) {
21         this.orderNum = orderNum;
22     }
23     
24 }
25 package org.jia;
26 
27 public class OrderItem {
28     private String orderdec;
29 
30     public String getOrderdec() {
31         return orderdec;
32     }
33 
34     public void setOrderdec(String orderdec) {
35         this.orderdec = orderdec;
36     }
37 }

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
    <bean id="orderItem" class="org.jia.OrderItem">
        <property name="orderdec" value="item00001"></property>
    </bean>
    <bean id="order" class="org.jia.Order" >
        <!-----注入变量 名字必须与类中的名字一样------->
        <property name="orderNum" value="order000007"></property>
         <！--注入对象 名字为orderitem，所属的类的应用id为orderItem-->
        <property name="orderitem" ref="orderItem"></property>
    
    --></bean>


</beans>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <!--此时的id就必须与Order.java中所定义的OrderItem的对象名称一样了，不然就会找不到-->
    <bean id="orderitem" class="org.jia.OrderItem">
        <property name="orderdec" value="item00001"></property>
    </bean>
    <bean id="order" class="org.jia.Order" autowire="byName">
        <property name="orderNum" value="order000007"></property>
    </bean>
</beans>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <!--按照byType注入则就与id没有关系，可以随便定义id ！！！但是不能出现多个此类的id-->
    <bean id="orderitdfadafaem" class="org.jia.OrderItem">
        <property name="orderdec" value="item00001"></property>
    </bean>
    <bean id="order" class="org.jia.Order" autowire="byType">
        <property name="orderNum" value="order000007"></property>
    </bean>
</beans>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="orderItem" class="org.jia.OrderItem">
        <property name="orderdec" value="item00001"></property>
    </bean>
    <bean id="order" class="org.jia.Order" autowire="constructor">
        <property name="orderNum" value="order000007"></property>
    </bean>
</beans>