Spring的懒加载机制原理和配置详解

<?xmlversion="1.0"encoding="UTF-8"?> 
<beansxmlns="//www.springframework.org/schema/beans" xmlns:xsi="//www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="//www.springframework.org/schema/beans //www.springframework.org/schema/beans/spring-beans-3.2.xsd"> 
<beanid="cart"class="cn.tedu.beans.Cart"lazy-init="true">
</bean>
</beans>

<?xmlversion="1.0"encoding="UTF-8"?> 
<beansxmlns="//www.springframework.org/schema/beans" xmlns:xsi="//www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="//www.springframework.org/schema/beans //www.springframework.org/schema/beans/spring-beans-3.2.xsd" default-lazy-init="true"> 
<beanid="cart"class="cn.tedu.beans.Cart">
    
</bean> 
</beans>

package ztt.lazy;
 
/**
 * @Description:
 * @Auther: tt
 * @Date: 2020/3/1 14:31
 */
public class Book {
    private String bookName;
 
    public Book() {
        System.out.println("调用构造方法，创建book...");
    }
 
    public String getBookName() {
        return bookName;
    }
 
    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
 
    @Override
    public String toString() {
        return "Book{" +
                "bookName='" + bookName + '\'' +
                '}';
    }
}

package ztt.lazy;
 
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
 
/**
 * @Description:
 * @Auther: tt
 * @Date: 2020/3/1 14:32
 */
public class Config {
 
    @Bean(value = "book")
    public Book getBook(){
        Book book = new Book();
        book.setBookName("《数据结构》");
        return book;
    }
 
    @Test
    public void test(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Config.class);
    }
}

    @Test
    public void test(){
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Config.class);
        System.out.println("初始化容器成功！");
        System.out.println("获取bean");
        Book book = (Book) applicationContext.getBean("book");
        System.out.println("从容器中取出book：");
        System.out.println(book);
    }