==================
Spring IoC应用案例
==================

在cn.tedu.springioc.beans包中添加Product类：

public class Product {
}

在cn.tedu.springioc.services包中添加ProductService接口：

public interface ProductService {
    public List<Product> queryProducts();
}

在cn.tedu.springioc.services.impl包中添加HotSellingProductService类：

public class HotSellingProductService implements ProductService {
    @Override
    public List<Product> queryProducts() {
        System.out.println("查询热销商品");
        return null;
    }
}

在cn.tedu.springioc.services.impl包中添加TopRatedProductService类：

public class TopRatedProductService implements ProductService {
    @Override
    public List<Product> queryProducts() {
        System.out.println("查询好评商品");
        return null;
    }
}

在cn.tedu.springioc.servlets包中添加ProductServlet类：

public class ProductServlet {
    private ProductService productService; // 仅接口，无对象

    public void setProductService(ProductService productService) {
        this.productService = productService;
    }

    public void doGet() {
        doPost();
    }

    public void doPost() {
        List<Product> products = productService.queryProducts(); // 面向接口
    }
}

添加对象配置：

<bean id="productService" class="cn.tedu.springioc.services.impl.HotSellingProductService" />
<bean id="productServlet" class="cn.tedu.springioc.servlets.ProductServlet" autowire="byName" />

测试：

public class SpringTest {
    public static void main(String[] args) {
        ...
        // 应用案例
        ProductServlet productServlet = context.getBean(
            "productServlet", ProductServlet.class);
        productServlet.doGet();
        ...
    }
}

查询热销商品

 __________Spring容器__________
|                              |
| HotSellingProductService --  |
|                          注| |
| ProductServlet           入| |
|     productService <-------  |
|______________________________|

更改对象配置：

<bean id="productService" class="cn.tedu.springioc.services.impl.TopRatedProductService" />

测试：

查询好评商品

 __________Spring容器__________
|                              |
| TopRatedProductService ----  |
|                          注| |
| ProductServlet           入| |
|     productService <-------  |
|______________________________|

Servlet无需关心究竟该实例化哪个Service实现，面向Service接口编程即可。

完全由配置文件，根据业务的实际需求，决定向Servlet注入哪个Service实现。

例程：SpringIoC