Spring实战——容器中的工程Bean

短命女 2021-07-24 23:56 443阅读 0赞

**一 配置**

<?xml version="1.0" encoding="GBK"?>
    <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://www.springframework.org/schema/beans"
         xsi:schemaLocation="http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">
         
         <bean id="north"  class="org.crazyit.app.factory.GetFieldFactoryBean">
               <property name="targetClass"  value="java.awt.BorderLayout"/>
               <property name="targetField" value="NORTH"/>
         </bean>
         
         <bean id="theValue"  class="org.crazyit.app.factory.GetFieldFactoryBean">
               <property name="targetClass"  value="java.sql.ResultSet"/>
               <property name="targetField"  value="TYPE_SCROLL_SENSITIVE"/>
         </bean>
    </beans>

**二 Bean工厂**

package org.crazyit.app.factory;
    
    
    import java.lang.reflect.*;
    import org.springframework.beans.factory.FactoryBean;
    
    public class GetFieldFactoryBean implements FactoryBean<Object>
    {
        private String targetClass;
        private String targetField;
        // targetClass的setter方法
        public void setTargetClass(String targetClass)
        {
            this.targetClass = targetClass;
        }
    
    
        // targetField的setter方法
        public void setTargetField(String targetField)
        {
            this.targetField = targetField;
        }
        // 返回工厂Bean所生产的产品
        public Object getObject() throws Exception
        {
            Class<?> clazz = Class.forName(targetClass);
            Field field = clazz.getField(targetField);
            return field.get(null);
        }
        // 获取工厂Bean所生产的产品的类型
        public Class<? extends Object> getObjectType()
        {
            return Object.class;
        }
        // 返回该工厂Bean所生成的产品是否为单例
        public boolean isSingleton()
        {
            return false;
        }
    }

**三 测试类**

package lee;
    
    
    import org.springframework.context.*;
    import org.springframework.context.support.*;
    
    
    public class SpringTest
    {
        public static void main(String[] args)throws Exception
        {
            ApplicationContext ctx = new
                ClassPathXmlApplicationContext("beans.xml");
            // 下面2行代码获取的FactoryBean的产品
            System.out.println(ctx.getBean("north"));
            System.out.println(ctx.getBean("theValue"));
            // 下面代码可获取的FactoryBean本身
            System.out.println(ctx.getBean("&theValue"));
        }
    }

**四 测试结果**

North
    1005
    org.crazyit.app.factory.GetFieldFactoryBean@56ac3a89

**五 说明**

java.awt.BorderLayout定义如下

public class BorderLayout implements LayoutManager2,
                                         java.io.Serializable {
    
        /**
         * The north layout constraint (top of container).
         */
        public static final String NORTH  = "North";
    }

java.sql.ResultSet定义如下

public interface ResultSet extends Wrapper, AutoCloseable {
        int TYPE_SCROLL_SENSITIVE = 1005;
    }