Spring @Qualifier注釋
有可能是當你創建同一類型的多個bean,並希望連線隻與屬性其中之一,在這種情況下,你可以使用@Qualifier注解一起@Autowired的通過指定其確切的bean來去除混亂的局麵將有線。下麵是一個例子,說明使用@ Qualifier注解。
例子:
讓我們使用Eclipse IDE,然後按照下麵的步驟來創建一個Spring應用程序:
步驟 | 描述 |
---|---|
1 | Create a project with a name SpringExample and create a package com.yiibai under the src folder in the created project. |
2 | Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter. |
3 | Create Java classes Student, Profile and MainApp under the com.yiibai package. |
4 | Create Beans configuration file Beans.xml under the src folder. |
5 | The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below. |
這裡是Student.java文件的內容:
package com.yiibai; public class Student { private Integer age; private String name; public void setAge(Integer age) { this.age = age; } public Integer getAge() { return age; } public void setName(String name) { this.name = name; } public String getName() { return name; } }
這裡是Profile.java文件的內容:
package com.yiibai; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; public class Profile { @Autowired @Qualifier("student1") private Student student; public Profile(){ System.out.println("Inside Profile constructor." ); } public void printAge() { System.out.println("Age : " + student.getAge() ); } public void printName() { System.out.println("Name : " + student.getName() ); } }
以下是MainApp.java文件的內容:
package com.yiibai; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml"); Profile profile = (Profile) context.getBean("profile"); profile.printAge(); profile.printName(); } }
請考慮下麵的配置文件beans.xml中的例子:
<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <context:annotation-config/> <!-- Definition for profile bean --> <bean id="profile" class="com.yiibai.Profile"> </bean> <!-- Definition for student1 bean --> <bean id="student1" class="com.yiibai.Student"> <property name="name" value="Zara" /> <property name="age" value="11"/> </bean> <!-- Definition for student2 bean --> <bean id="student2" class="com.yiibai.Student"> <property name="name" value="Nuha" /> <property name="age" value="2"/> </bean> </beans>
創建源代碼和bean配置文件完成後,讓我們運行應用程序。如果一切順利,這將打印以下信息:
Inside Profile constructor. Age : 11 Name : Zara