思路分析

》》1：查詢redis，沒有json資料，就呼叫CategoryDao，去獲取集合List<Category>
先回傳給CategorySrvice，再轉成json存進redis
》》2：第二次起，直接獲取redis中的json，將json轉成List<Category>

(1) 撰寫CategoryServiceTest

test\java\com\wzx\pack01\TestCategoryService.java

//第一步：測驗開發CategoryService
public class TestCategoryService {
    @Test
    public void test01() throws Exception {

        //0: 創建業務類物件
        CategoryService categoryService = new CategoryService();

        //1: 查詢分類集合
        List<Category> list = categoryService.queryAll();

        for(Category category:list){
            System.out.println(category);
        }


    }
}

(2)撰寫javaBean與CategoryDao

src\com\wzx\bean\Category.java

//第二步驟 ：
public class Category {
    private int cid;
    private String cname;

src\com\wzx\dao\CategoryDao.java

public class CategoryDao {
    public List<Category> findAll() {
        //1：創建集合
        List<Category> list = new ArrayList<>();
        //使用回圈模擬資料，以后使用mybatis來查資料
        for (int i = 0; i < 10; i++) {
            list.add(new Category(i,"分類名"+i));
        }
        return list;
    }
}

(3)撰寫CategoryService

src\com\wzx\service\CategoryService.java

//第三步驟：實作queryAll方法
//3.1 復制jedis jar過來
//3.2 系結
//3.3 復制properties檔案，與工具類
public class CategoryService {
    CategoryDao dao = new CategoryDao();
    ObjectMapper objectMapper = new ObjectMapper();
    public List<Category> queryAll() throws IOException {
        //queryAll的邏輯
        //1：先訪問redis，有資料就回傳 JedisUtils  Map<Srting,String>
        //3.4獲取連接
        Jedis redis = JedisUtils.getRedis();
        //快取
        String json = redis.get("list");
        if(json == null){
            System.out.println("第一次查詢 redis沒有資料，查的資料庫的資料，慢");
            //2: 沒有資料就查詢資料，進行快取，方便下次使用 CategoryDao
            List<Category> list = dao.findAll();
            //快取  將集合轉換成json，快取到redis
            //3.5 添加json jar到lib目錄并且系結
            //3.6 創建ObjectMapper物件，轉list成json
            String jsonValue =  objectMapper.writeValueAsString(list);

            System.out.println(jsonValue);

            redis.set("list",jsonValue);
            return list;
        }else{//json ! =null
            System.out.println("第二次 redis有資料，直接回傳，快");
            List<Category> list = objectMapper.readValue(json,new TypeReference<List<Category>>(){});//將json轉成物件   參1 json資料  參2
            return list;
        }

    }
}

(4)將json資料轉成物件

test\java\com\wzx\pack01\TestObjectMapper.java

public class TestObjectMapper {
    @Test
    public void test01() throws IOException {
        String json="[{\"cid\":0,\"cname\":\"分類名0\"},{\"cid\":1,\"cname\":\"分類名1\"},{\"cid\":2,\"cname\":\"分類名2\"},{\"cid\":3,\"cname\":\"分類名3\"},{\"cid\":4,\"cname\":\"分類名4\"},{\"cid\":5,\"cname\":\"分類名5\"},{\"cid\":6,\"cname\":\"分類名6\"},{\"cid\":7,\"cname\":\"分類名7\"},{\"cid\":8,\"cname\":\"分類名8\"},{\"cid\":9,\"cname\":\"分類名9\"}]";

        //
        ObjectMapper objectMapper = new ObjectMapper();

        List<Category> list = objectMapper.readValue(json,new TypeReference<List<Category>>(){});//將json轉成物件   參1 json資料  參2 new TypeReference<>(){}
        System.out.println(list);
    }
}

• 參2 new TypeReference<回傳值型別>(){}

(5)過濾器解決全站中文編碼亂碼

src\com\wzx\filter\CharSetFilter.java

@WebFilter("/*")
public class CharSetFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}

(6)解決Servlet顯示分類串列

src\com\wzx\servlet\CategoryListServlet.java

@WebServlet("/list")
public class CategoryListServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //0: 創建業務類物件
        CategoryService categoryService = new CategoryService();

        //1: 查詢分類集合
        List<Category> list = categoryService.queryAll();

        //2: 請求轉發
        request.setAttribute("list",list);
        request.getRequestDispatcher("list.jsp").forward(request,response);

    }
}

web\list.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 <html>
<head>
    <title>Title</title>
</head>
<body>
        <c:forEach items="${list}" var="item">
           <div > ${item.cname} </div>
        </c:forEach>
</body>
</html>

(7)其他

Lib

jedis.properties

maxTotal=30
maxIdle=10
url=localhost
port=6379

JedisUtils

src\com\wzx\util\JedisUtils.java

public class JedisUtils {
    private static JedisPool pool = null;
    //1:創建一個連接池
    static{
        //1.1 決議properties檔案
        ResourceBundle bundle = ResourceBundle.getBundle("jedis");
        //獲取引數
        String maxTotal = bundle.getString("maxTotal");
        String maxIdle = bundle.getString("maxIdle");
        String url = bundle.getString("url");
        String port = bundle.getString("port");

        //1.2創建連接池
        //1:創建連接池的配置物件
        JedisPoolConfig config = new JedisPoolConfig();
        //1.1 設定最大連接數
        config.setMaxTotal(Integer.parseInt(maxTotal));
        //1.2 設定空閑連接數
        config.setMaxIdle(Integer.parseInt(maxIdle));

        //2:創建連接池
         pool = new JedisPool(config, url, Integer.parseInt(port));
    }

    //2:對外提供一個獲取連接的方法
    public static Jedis getJedis(){
        return  pool.getResource();
    }

    //3:提供釋放資源的方法
    public static void close(Jedis jedis){
        if(jedis != null) {
            jedis.close();
        }
    }
}