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 )
getter&setter方式的注入
· autowire="defualt"
· autowire=“byName”
· autowire="bytype"
详细解析注入方式
例如:有如下两个类需要注入
第一个类:
public class Order {
private String orderNum;
@SuppressWarnings ( "unused" )
private OrderItem orderitem;
public OrderItem getOrderitem() {
return orderitem;
}
public void setOrderitem(OrderItem orderitem) {
this .orderitem = orderitem;
}
public String getOrderNum() {
return orderNum;
}
public void setOrderNum(String orderNum) {
this .orderNum = orderNum;
}
}
第二个类:
public class OrderItem {
private String orderdec;
public String getOrderdec() {
return orderdec;
}
public void setOrderdec(String orderdec) {
this .orderdec = orderdec;
}
}
常用getter&&setter方式介绍
方式第一种注入:
<? 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 >
方式第二种注入: byName
<? 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" < span style = "color: #ff0000;" > autowire = "byName" </ span > >
< property name = "orderNum" value = "order000007" > </ property >
</ bean >
</ beans >
方式第三种注入: byType
<? 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" < span style = "color: #ff0000;" > autowire = "byType" </ span > >
< property name = "orderNum" value = "order000007" > </ property >
</ bean >
</ beans >
autowire="constructor"
需要在 Order.java 中加入一个构造器
public Order(OrderItem item ) {
orderitem = item;
}
XML配置文件
<? 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 >
三种注入方式比较
接口注入:
接口注入模式因为具备侵入性,它要求组件必须与特定的接口相关联,因此并不被看好,实际使用有限。
Setter 注入:对于习惯了传统 javabean 开发的程序员,通过 setter 方法设定依赖关系更加直观。如果依赖关系较为复杂,那么构造子注入模式的构造函数也会相当庞大,而此时设值注入模式则更为简洁。如果用到了第三方类库,可能要求我们的组件提供一个默认的构造函数,此时构造子注入模式也不适用。构造器注入:在构造期间完成一个完整的、合法的对象。所有依赖关系在构造函数中集中呈现。依赖关系在构造时由容器一次性设定,组件被创建之后一直处于相对“不变”的稳定状态。只有组件的创建者关心其内部依赖关系,对调用者而言,该依赖关系处于“黑盒”之中。