<!--开启 cache 缓存-->
   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-cache</artifactId>
   </dependency>
   <!-- ehcache 缓存 -->
   <dependency>
     <groupId>net.sf.ehcache</groupId>
     <artifactId>ehcache</artifactId>
   </dependency>

<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="http://ehcache.org/ehcache.xsd"
     updateCheck="false">
  <defaultCache
      eternal="false"
      maxElementsInMemory="1000"
      overflowToDisk="false"
      diskPersistent="false"
      timeToIdleSeconds="0"
      timeToLiveSeconds="600"
      memoryStoreEvictionPolicy="LRU" />

  <!-- 这里的 users 缓存空间是为了下面的 demo 做准备 -->
  <cache
      name="users"
      eternal="false"
      maxElementsInMemory="100"
      overflowToDisk="false"
      diskPersistent="false"
      timeToIdleSeconds="0"
      timeToLiveSeconds="300"
      memoryStoreEvictionPolicy="LRU" />
</ehcache>

public class User {

  private long id;
  private String uuid;
  private String name;
  private Integer age;

  //省略 get、set 及 toString 方法
}

@Mapper
public interface UserDao{

  void delete(String uuid);

  User update(User user);

  User findByUuid(String uuid);

  int save(@Param("user") User user);
}

<?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="qg.fangrui.boot.dao.UserDao">
  <!--目的：为Dao接口方法提供SQL语句-->

  <!--映射实体对象-->
  <resultMap id="UserResultMap" type="qg.fangrui.boot.model.User">
    <id property="id" column="id" />
    <result property="uuid" column="uuid" />
    <result property="name" column="name" />
    <result property="age" column="age" />
  </resultMap>


  <insert id="save">
    INSERT INTO users(name, age, uuid)
    VALUES (#{user.name}, #{user.age}, #{user.uuid})
  </insert>

  <select id="findByUuid" resultType="User">
    SELECT * FROM users WHERE uuid = #{uuid}
  </select>

  <delete id="delete">
    DELETE FROM users WHERE uuid = #{uuid}
  </delete>

</mapper>

@Service
public class UserService {

  //这里的单引号不能少，否则会报错，被识别是一个对象
  private static final String CACHE_KEY = "'user'";
  private static final String DEMO_CACHE_NAME = "users";

  @Autowired
  private UserDao userDao;

  //删除用户数据
  @CacheEvict(value = DEMO_CACHE_NAME,key = "'user_'+#uuid")//这是清除缓存
  public void delete(String uuid){
    userDao.delete(uuid);
  }

  //更新用户数据
  @CachePut(value = DEMO_CACHE_NAME,key = "'user_'+#user.getUuid()")
  public User update(User user) throws CacheException{
    User user1 = userDao.findByUuid(user.getUuid());
    if (null == user1){
      throw new CacheException("Not Find");
    }
    user1.setAge(user.getAge());
    user1.setName(user.getName());
    return user1;
  }

  //查找用户数据
  @Cacheable(value=DEMO_CACHE_NAME,key="'user_'+#uuid")
  public User findByUuid(String uuid){
    //若找不到缓存将打印出提示语句
    System.err.println("没有走缓存！"+uuid);
    return userDao.findByUuid(uuid);
  }

  //保存用户数据
  @CacheEvict(value=DEMO_CACHE_NAME,key=CACHE_KEY)
  public int save(User user){
    return userDao.save(user);
  }
}

@RestController
public class EhcacheController {

  private static final Logger logger = LoggerFactory.getLogger(EhcacheController.class);

  @Autowired
  private UserService userService;

  @RequestMapping("/encache")
  public String EhcacheTest(){
    logger.debug("进行Encache缓存测试");
    System.out.println("====生成第一个用户====");
    User user1 = new User();
    //生成第一个用户的唯一标识符 UUID
    String u1_uuid = UUID.randomUUID().toString();
    //去掉 UUID 的 - 符号
    String uuid1 = u1_uuid.substring(0,8)+u1_uuid.substring(9,13)+u1_uuid.substring(14,18)+u1_uuid.substring(19,23)+u1_uuid.substring(24);
    user1.setName("张三");
    user1.setAge(18);
    user1.setUuid(uuid1);
    if (userService.save(user1) == 0){
      throw new JdbcException("用户对象插入数据库失败");
    }

    //第一次查询
    System.out.println(userService.findByUuid(user1.getUuid()));
    //通过缓存查询
    System.out.println(userService.findByUuid(user1.getUuid()));

    System.out.println("====修改数据====");
    User user2 = new User();
    user2.setName("李四-update");
    user2.setAge(22);
    user2.setId(user1.getId());
    user2.setUuid(user1.getUuid());
    try {
      System.out.println(userService.update(user2));
    } catch (CacheException e){
      e.printStackTrace();
    }

    System.out.println(userService.findByUuid(user2.getUuid()));
    return "success";
  }
}