spring_(5)XML配置裡的Bean自動裝配
阿新 • • 發佈:2018-12-21
- SpringIOC容器可以自動裝配Bean.需要做的僅僅是在的autowire屬性裡指定自動裝配的模式
- byType(根據型別自動裝配):若IOC容器中有多個與目標Bean型別一致的Bean.在這種情況下,Spring將無法判定哪個Bean最適合該屬性,所以不能執行自動裝配
- byName(根據名稱自動裝配):必須將目標Bean的名稱和屬性名設定的完全相同
- constructor(通過構造器自動裝配):當Bean中存在多個構造器時,此種自動裝配方式將會很複雜,不推薦使用
XML配置裡的Bean自動裝配的缺點
- 在Bean配置檔案裡設定autowire屬性進行自動裝配將會裝配Bean的所有屬性。然而,若只希望裝配個別屬性時,autowire屬性就不夠靈活了。
- autowire屬性要麼根據型別自動裝配,要麼根據名稱自動裝配,不能兩者兼而有之。
- 一般情況下,在實際的專案中很少使用自動裝配功能,因為和自動裝配功能所帶來的好處比起來,明確清晰的配置文件更有說服力一些。
例子程式:
程式的結構
Address.java
package com.spring.beans.autowire;
public class Address {
private String city;
private String street;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
@Override
public String toString() {
return "Address{" +
"city='" + city + '\'' +
", street='" + street + '\'' +
'}';
}
}
Car.java
package com.spring.beans.autowire;
public class Car {
private String brand;
private double price;
public String getBrand() {
return brand;
}
public void setBrand(String brand) {
this.brand = brand;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
@Override
public String toString() {
return "Car{" +
"brand='" + brand + '\'' +
", price=" + price +
'}';
}
}
Person.java
package com.spring.beans.autowire;
public class Person {
private String name;
private Address address;
private Car car;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public Car getCar() {
return car;
}
public void setCar(Car car) {
this.car = car;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", address=" + address +
", car=" + car +
'}';
}
}
beans-autowire.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"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id = "address" class="com.spring.beans.autowire.Address"
p:city="BeiJing" p:street="HuiLongGuan"></bean>
<bean id = "address2" class="com.spring.beans.autowire.Address"
p:city="DaLian" p:street="ZhongShan"></bean>
<bean id="car" class="com.spring.beans.autowire.Car"
p:brand="Audi" p:price="300000"></bean>
<!--
之前的配置方法
<bean id="person" class="com.spring.beans.autowire.Person" p:name="Tom" p:address-ref="address" p:car-ref="car"></bean>
-->
<!--
可以使用autowire 屬性指定自動裝配的方式
byName 根據 bean 的名字和當前bean的setter風格的屬性名進行自動裝配,若有匹配的,則進行自動裝配若沒有匹配的,則不裝配
byType 根據 bean 的型別和當前bean的屬性的型別進行自動裝配。若IOC 容器中有1個以上的型別匹配的bean,則拋異常。
-->
<bean id="person" class="com.spring.beans.autowire.Person"
p:name="Tom" autowire="byName"></bean>
<!--<bean id="person" class="com.spring.beans.autowire.Person"
p:name="Tom" autowire="byType"></bean>
這裡會報錯,因為byType要求只有一個相關bean,而現在有兩個address-->
</beans>
Main.java
package com.spring.beans.autowire;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Main {
public static void main(String[] args){
ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-autowire.xml");
Person person = (Person)ctx.getBean("person");
System.out.println(person);
}
}