相關文章
Dependency Injection
概念
- 依賴注入（DI）
- 依賴：指Bean對象的創建依賴於容器。Bean對象的依賴資源
- 注入：指Bean對象
注入方式
一共有三種：分別是構造器注入；Set注入；P命名和C命名注入
構造器注入
在Spring從入門到入土——快速上手Spring中Beans.xml中有詳細介紹
<?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
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 第一種根據參數名字來設置-->
<bean id="userT" class="com.zhonghu.pojo.UserT">
<!-- name 指參數名-->
<constructor-arg name="name"value="zhonghu"/>
</bean>
<!-- 第二種根骨index參數下標來設置-->
<bean id="userT" class="com.zhonghu.pojo.UserT">
<!-- index值構造方法，下標從0開始 -->
<constructor-arg index="0" value="zhonghu"/>
</bean>
<!-- 第三種 根據參數類型設置 十分不推薦-->
<bean id="useT"class="com.zhonghu.pojo.UserT">
<constructor-arg type="java.lang.String" value="zhonghu"/>
</bean>
</beans>
Set注入
要求被注入的屬性必須有set方法，set方法的方法名由set + 屬性首字母大寫 , 如果屬性是boolean類型 , 沒有set方法 , 是 is
測試pojo類：
Address.java
public class Address {
private String Address;
public String getAddress() {
return Address;
}
public void setAddress(String address) {
Address = address;
}
@Override
public String toString() {
return "Address{" +
"Address='" + Address + '\'' +
'}';
}
}
Student.java
public class Student {
private String name;
private Address address;
private String[] books;
private List<String> hobbies;
private Map<String,String> card;
private Set<String> games;
private String wife;
private Properties info;
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 String[] getBooks() {
return books;
}
public void setBooks(String[] books) {
this.books = books;
}
public List<String> getHobbies() {
return hobbies;
}
public void setHobbies(List<String> hobbies) {
this.hobbies = hobbies;
}
public Map<String, String> getCard() {
return card;
}
public void setCard(Map<String, String> card) {
this.card = card;
}
public Set<String> getGames() {
return games;
}
public void setGames(Set<String> games) {
this.games = games;
}
public String getWife() {
return wife;
}
public void setWife(String wife) {
this.wife = wife;
}
public Properties getInfo() {
return info;
}
public void setInfo(Properties info) {
this.info = info;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", address=" + address.toString() +
", books=" + Arrays.toString(books) +
", hobbies=" + hobbies +
", card=" + card +
", games=" + games +
", wife='" + wife + '\'' +
", info=" + info +
'}';
}
}
Bean注入：
beans.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
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="address" class="com.zhonghu.pojo.Address">
<property name="address" value="China"/>
</bean>
<bean id="student" class="com.zhonghu.pojo.Student">
<!-- 普通值注入-->
<property name="name" value="冢狐"/>
<!-- Bean注入-->
<property name="address" ref="address"/>
<!-- 數組 -->
<property name="books">
<array>
<value>紅樓夢</value>
<value>三國演義</value>
<value>水滸傳</value>
<value>西遊記</value>
</array>
</property>
<!-- list-->
<property name="hobbies">
<list>
<value>打遊戲</value>
<value>看電影</value>
<value>碼代碼</value>
</list>
</property>
<!-- map-->
<property name="card">
<map>
<entry key="學號" value="123456789"/>
<entry key="性別" value="男"/>
<entry key="姓名" value="冢狐"/>
</map>
</property>
<!-- set-->
<property name="games">
<set>
<value>CSGO</value>
<value>COC</value>
</set>
</property>
<!-- Null-->
<property name="wife">
<null/>
</property>
<!-- Properties-->
<property name="info">
<props>
<prop key="url">https://blog.csdn.net/issunmingzhi</prop>
<prop key="用戶名">root</prop>
<prop key="密碼">123456</prop>
</props>
</property>
</bean>
</beans>
測試：
public class MyTest {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Student student = (Student) context.getBean("student");
System.out.println(student.toString());
}
}
結果：
p命名和c命名注入
user.java：【注意，這裏沒有有參構造器】
public class User {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
p命名空間注入：
就是set注入、需要在頭文件中加入約束條件
導入約束 : xmlns:p="http://www.springframework.org/schema/p"
<!--P(屬性: properties)命名空間 , 屬性依然要設置set方法-->
<bean id="user" class="com.zhonghu.pojo.User" p:name="冢狐" p:age="18"/>
c命名空間注入
就是構造器注入、需要在頭文件下加入約束文件
導入約束 : xmlns:c="http://www.springframework.org/schema/c"
<!--C(構造: Constructor)命名空間 , 屬性依然要設置set方法-->
<bean id="user" class="com.kuang.zhonghu.User" c:name="冢狐" c:age="18"/>
此時會發現出問題：因爲沒有寫有參構造函數
C命名空間注入就是所謂的構造器注入