思路分析
》》1：查询redis，没有json数据，就调用CategoryDao，去获取集合List<Category>
先返回给CategorySrvice，再转成json存进redis
》》2：第二次起，直接获取redis中的json，将json转成List<Category>
(1) 编写CategoryServiceTest
test\java\com\wzx\pack01\TestCategoryService.java
//第一步：测试开发CategoryService
public class TestCategoryService {
@Test
public void test01() throws Exception {
//0: 创建业务类对象
CategoryService categoryService = new CategoryService();
//1: 查询分类集合
List<Category> list = categoryService.queryAll();
for(Category category:list){
System.out.println(category);
}
}
}
(2)编写javaBean与CategoryDao
src\com\wzx\bean\Category.java
//第二步骤 ：
public class Category {
private int cid;
private String cname;
src\com\wzx\dao\CategoryDao.java
public class CategoryDao {
public List<Category> findAll() {
//1：创建集合
List<Category> list = new ArrayList<>();
//使用循环模拟数据，以后使用mybatis来查数据
for (int i = 0; i < 10; i++) {
list.add(new Category(i,"分类名"+i));
}
return list;
}
}
(3)编写CategoryService
src\com\wzx\service\CategoryService.java
//第三步骤：实现queryAll方法
//3.1 复制jedis jar过来
//3.2 绑定
//3.3 复制properties文件，与工具类
public class CategoryService {
CategoryDao dao = new CategoryDao();
ObjectMapper objectMapper = new ObjectMapper();
public List<Category> queryAll() throws IOException {
//queryAll的逻辑
//1：先访问redis，有数据就返回 JedisUtils Map<Srting,String>
//3.4获取连接
Jedis redis = JedisUtils.getRedis();
//缓存
String json = redis.get("list");
if(json == null){
System.out.println("第一次查询 redis没有数据，查的数据库的数据，慢");
//2: 没有数据就查询数据，进行缓存，方便下次使用 CategoryDao
List<Category> list = dao.findAll();
//缓存 将集合转换成json，缓存到redis
//3.5 添加json jar到lib目录并且绑定
//3.6 创建ObjectMapper对象，转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有数据，直接返回，快");
List<Category> list = objectMapper.readValue(json,new TypeReference<List<Category>>(){
});//将json转成对象 参1 json数据 参2
return list;
}
}
}
(4)将json数据转成对象
test\java\com\wzx\pack01\TestObjectMapper.java
public class TestObjectMapper {
@Test
public void test01() throws IOException {
String json="[{\"cid\":0,\"cname\":\"分类名0\"},{\"cid\":1,\"cname\":\"分类名1\"},{\"cid\":2,\"cname\":\"分类名2\"},{\"cid\":3,\"cname\":\"分类名3\"},{\"cid\":4,\"cname\":\"分类名4\"},{\"cid\":5,\"cname\":\"分类名5\"},{\"cid\":6,\"cname\":\"分类名6\"},{\"cid\":7,\"cname\":\"分类名7\"},{\"cid\":8,\"cname\":\"分类名8\"},{\"cid\":9,\"cname\":\"分类名9\"}]";
//
ObjectMapper objectMapper = new ObjectMapper();
List<Category> list = objectMapper.readValue(json,new TypeReference<List<Category>>(){
});//将json转成对象 参1 json数据 参2 new TypeReference<>(){}
System.out.println(list);
}
}
- 参2 new TypeReference<返回值类型>(){}
(5)过滤器解决全站中文编码乱码
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)解决Servlet显示分类列表
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: 创建业务类对象
CategoryService categoryService = new CategoryService();
//1: 查询分类集合
List<Category> list = categoryService.queryAll();
//2: 请求转发
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:创建一个连接池
static{
//1.1 解析properties文件
ResourceBundle bundle = ResourceBundle.getBundle("jedis");
//获取参数
String maxTotal = bundle.getString("maxTotal");
String maxIdle = bundle.getString("maxIdle");
String url = bundle.getString("url");
String port = bundle.getString("port");
//1.2创建连接池
//1:创建连接池的配置对象
JedisPoolConfig config = new JedisPoolConfig();
//1.1 设置最大连接数
config.setMaxTotal(Integer.parseInt(maxTotal));
//1.2 设置空闲连接数
config.setMaxIdle(Integer.parseInt(maxIdle));
//2:创建连接池
pool = new JedisPool(config, url, Integer.parseInt(port));
}
//2:对外提供一个获取连接的方法
public static Jedis getJedis(){
return pool.getResource();
}
//3:提供释放资源的方法
public static void close(Jedis jedis){
if(jedis != null) {
jedis.close();
}
}
}