redis实现简单的条件查询(2)-木庄网络博客

由于Redis是nosql,无法直接像mysql那样利用where进行条件查询,所以Redis想实现条件查询,只能用一个笨方法:将所有符合条件的user存到一个set中。

Jedis jedis = new Jedis("127.0.0.1",6379);
    Map<String, String> map = new HashMap<String,String>();
     
    final String USER_TABLE = "USER_TABLE";
    //查询年龄为15,性别为n
     
    final String USER_TABLE_AGE_15 = "USER_TABLE_AGE_15";
    final String USER_TABLE_SEX_m = "USER_TABLE_SEX_m";
    final String USER_TABLE_SEX_n = "USER_TABLE_SEX_n";
     
    //向缓存中存入5条数据组成的map
     
    String uuid1 = UUID.randomUUID().toString();
    User user1 = new User(uuid1, "y1", "m", 15);
    //将对象转为json
    map.put(uuid1, JSONObject.fromObject(user1).toString());
    //将符合条件的user的Id存到set中
    jedis.sadd(USER_TABLE_AGE_15,uuid1);
    jedis.sadd(USER_TABLE_SEX_m,uuid1);
     
    String uuid2 = UUID.randomUUID().toString();
    User user2 = new User(uuid2, "y2", "m", 18);
    map.put(uuid2, JSONObject.fromObject(user2).toString());
    jedis.sadd(USER_TABLE_SEX_m,uuid2);
     
    String uuid3 = UUID.randomUUID().toString();
    User user3 = new User(uuid3, "y3", "n", 25);
    map.put(uuid3, JSONObject.fromObject(user3).toString());
     
    String uuid4 = UUID.randomUUID().toString();
    User user4 = new User(uuid4, "y4", "n", 15);
    map.put(uuid4, JSONObject.fromObject(user4).toString());
    jedis.sadd(USER_TABLE_AGE_15,uuid4);
     
    String uuid5 = UUID.randomUUID().toString();
    User user5 = new User(uuid5, "y5", "m", 25);
    map.put(uuid5, JSONObject.fromObject(user5).toString());
    jedis.sadd(USER_TABLE_SEX_m,uuid5);
     
    //把map存到缓存中
    jedis.hmset("USER_TABLE", map);

那么,如果想要查询年龄为15的user,就需要先从USER_TABLE_AGE_15中取出所有的uuid,然后再从USER_TABLE中取出user

//获取年龄为15的user的uuid
Set<String> age = jedis.smembers(USER_TABLE_AGE_15);
 
//根据uuid获取user
List<User> userJson = new ArrayList<User>();
 
for (Iterator iterator = age.iterator(); iterator.hasNext();) {
    String string = (String) iterator.next();
    String jsonStr = jedis.hget(USER_TABLE, string);
    JSONObject json = JSONObject.fromObject(jsonStr);
    User user = (User) JSONObject.toBean(json, User.class);
    userJson.add(user);
    System.out.println(user);
}

结果如下:

1 2	`User [id=63a970ec-e997-43e0-8ed9-14c5eb87de8b, name=y1, sex=m, age=15]` `User [id=aa074a2a-88d9-4b50-a99f-1375539164f7, name=y4, sex=n, age=15]`

那么如果现在需要年龄为15,性别为m的user呢,很简单,获取
USER_TABLE_AGE_15 和 USER_TABLE_SEX_m的并集,再从USER_TABLE中获取.

//获取年龄为15并性别为m的user
    Set<String> userSet = jedis.sinter(USER_TABLE_AGE_15,USER_TABLE_SEX_m);
    List<User> users = new ArrayList<User>();
    for (Iterator iterator = userSet.iterator(); iterator.hasNext();) {
        String string = (String) iterator.next();
        String jsonStr = jedis.hget(USER_TABLE, string);
        JSONObject json = JSONObject.fromObject(jsonStr);
        User user = (User) JSONObject.toBean(json, User.class);
        users.add(user);
        System.out.println(user);
    }