1、使用構造器創建bean
1.1、使用無參構造器創建
package com.ly.spring; public class Person { private String name; public void say(String name) { System.out.println("你好，我叫"+name); } }
<?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"> <!--若沒有無參構造器會報錯--> <bean id="person" class="com.ly.spring.Person"></bean> </beans>
1.2、使用有參構造器創建
package com.ly.spring; public class Person { private String name; public Person(String name) { this.name = name; } public void say() { System.out.println("我的名字叫"+this.name); } }
<?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="person" class="com.ly.spring.Person"> <!--指定構造器對應引數名對應的值--> <constructor-arg name="name" value="有參構造"></constructor-arg> </bean> </beans>
2、使用靜態工廠方法創建bean
Person:
package com.ly.spring; public class Person { private String name; public Person(String name) { this.name = name; } public void say() { System.out.println("我的名字叫"+this.name); } }
Chinese:
package com.ly.spring; public class Chinese implements Person { private String name; public void setName(String name) { this.name = name; } @Override public void say() { System.out.println("我的名字叫"+this.name); } }
American:
package com.ly.spring; public class American implements Person { private String name; public void setName(String name) { this.name = name; } @Override public void say() { System.out.println("我的名字叫"+this.name); } }
工廠類PersonFactory:
package com.ly.spring; public class PersonFactory { public static Person getPerson(String name) { if("Chinese".equals(name)) { return new Chinese(); }else if("American".equals(name)) { return new American(); } return null; } }
組態檔：
<?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"> <!-- class指定工廠類類路徑 factory-method指定工廠類的靜態方法 --> <bean id="chinese" class="com.ly.spring.PersonFactory" factory-method="getPerson"> <!--給工廠的靜態方法注入引數--> <constructor-arg name="name" value="Chinese"></constructor-arg> <!--通過set方法給Chinese類的name屬性注入值--> <property name="name" value="中國人"></property> </bean> <bean id="american" class="com.ly.spring.PersonFactory" factory-method="getPerson"> <constructor-arg name="name" value="American"></constructor-arg> <property name="name" value="美國人"></property> </bean> </beans>
測驗類：
package com.ly.spring.test; import com.ly.spring.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainTest { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml"); Person p1 = context.getBean("chinese", Person.class);//獲取到的其實是Chinese類 p1.say();//執行時會呼叫Chinese類的方法 Person p2 = context.getBean("american",Person.class);//獲取到的其實是American類 p2.say();//執行時會呼叫American類的方法 } }
3、使用實體工廠方法創建bean
修改后的工廠類PersonFactory:
package com.ly.spring; public class PersonFactory { //這里不再是靜態方法 public Person getPerson(String name) { if("Chinese".equals(name)) { return new Chinese(); }else if("American".equals(name)) { return new American(); } return null; } }
修改后的組態檔：
<?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"> <!--配置工廠bean--> <bean id="personFactory" class="com.ly.spring.PersonFactory"></bean> <!-- factory-bean指定配置的工廠bean factory-method指定工廠類的實體方法 --> <bean id="chinese" factory-bean="personFactory" factory-method="getPerson"> <!--給工廠的實體方法注入引數--> <constructor-arg name="name" value="Chinese"></constructor-arg> <!--通過set方法給Chinese類的name屬性注入值--> <property name="name" value="中國人"></property> </bean> <bean id="american" factory-bean="personFactory" factory-method="getPerson"> <constructor-arg name="name" value="American"></constructor-arg> <property name="name" value="美國人"></property> </bean> </beans>
4、擴展：利用工廠bean的知識注入Date型別的屬性
Person:
package com.ly.spring; import java.util.Date; public class Person { private Date birthday; public void setBirthday(Date birthday) { this.birthday = birthday; } public void showBirthday() { System.out.println("我的生日是："+this.birthday); } }
組態檔：
<?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"> <!--SimpleDateFormat可看作日期的工廠bean--> <bean id="simpleDateFormat" class="java.text.SimpleDateFormat"> <constructor-arg name="pattern" value="yyyy-MM-dd HH:mm:ss"></constructor-arg> </bean> <bean id="date" factory-bean="simpleDateFormat" factory-method="parse"> <constructor-arg name="source" value="2020-02-19 13:17:30"></constructor-arg> </bean> <bean id="person" class="com.ly.spring.Person"> <!--使用Person類的set方法注入屬性值--> <property name="birthday" ref="date"></property> </bean> </beans>
測驗類：
package com.ly.spring.test; import com.ly.spring.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainTest { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml"); Person person = context.getBean("person",Person.class); person.showBirthday(); } }
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