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：

1package com.jbjf.work.fourierbackstage.service.Impl;
2
3import java.util.List;
4
5import org.springframework.beans.factory.annotation.Autowired;
6import org.springframework.stereotype.Service;
7
8import com.jbjf.work.fourierbackstage.dao.ProductDao;
9import com.jbjf.work.fourierbackstage.model.Product;
10import com.jbjf.work.fourierbackstage.service.ProductService;
11
12@Service("productService")
13public class ProductServiceImpl implements ProductService {
14
15    @Autowired
16    private ProductDao productDao;
17    @Override
18    public List<Product> defaultProductList() {
19        return productDao.defaultProductList();
20    }
21}

··web层，就是具体的实现，其将数据库的操作交给对应的mapper

1package com.jbjf.work.fourierbackstage.web;
2
3import java.util.ArrayList;
4import java.util.List;
5
6import javax.servlet.http.HttpServletRequest;
7
8import org.springframework.beans.factory.annotation.Autowired;
9import org.springframework.stereotype.Controller;
10import org.springframework.web.bind.annotation.RequestMapping;
11
12import com.jbjf.work.fourierbackstage.model.Product;
13import com.jbjf.work.fourierbackstage.service.ProductService;
14
15@Controller
16public class ProductController {
17
18    @Autowired
19    private ProductService productService;
20    @RequestMapping("productList")
21    public String productList(HttpServletRequest request){
22        List<Product> defaultProductList = new ArrayList();
23        defaultProductList = productService.defaultProductList();
24        int productCount = productService.getProductCount();
25        request.setAttribute("defaultProductList", defaultProductList);
26        return "productList";
27    }
28}

mapper：

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