ssm 不能将查询的结果返回到界面的一个原因

* 在controller类中，应先定义一个ArrayList的集合即就是：

List<Product> defaultProductList = new ArrayList(); // 实体类未Product

其他的模块如下

·· dao、service都是定义的方法名

·· service的实现类返回dao的方法，即就是：

package com.jbjf.work.fourierbackstage.service.Impl;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.jbjf.work.fourierbackstage.dao.ProductDao;
import com.jbjf.work.fourierbackstage.model.Product;
import com.jbjf.work.fourierbackstage.service.ProductService;

@Service("productService")
public class ProductServiceImpl implements ProductService {

    @Autowired
    private ProductDao productDao;
    @Override
    public List<Product> defaultProductList() {
        return productDao.defaultProductList();
    }
}

··web层，就是具体的实现，其将数据库的操作交给对应的mapper

package com.jbjf.work.fourierbackstage.web;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.jbjf.work.fourierbackstage.model.Product;
import com.jbjf.work.fourierbackstage.service.ProductService;

@Controller
public class ProductController {

    @Autowired
    private ProductService productService;
    @RequestMapping("productList")
    public String productList(HttpServletRequest request){
        List<Product> defaultProductList = new ArrayList();
        defaultProductList = productService.defaultProductList();
        int productCount = productService.getProductCount();
        request.setAttribute("defaultProductList", defaultProductList);
        return "productList";
    }
}

mapper：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jbjf.work.fourierbackstage.dao.ProductDao">
    <select id="defaultProductList" resultType="com.jbjf.work.fourierbackstage.model.Product">
        select * from jbjf_product
    </select>
</mapper>