一、导入jar包
二、实现简单的条件查询
创建一个User实体类
public class User { private String id; private String name; private String sex; private int age; public String getId() { return id; } public User() { super(); } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public User(String id, String name, String sex, int age) { super(); this.id = id; this.name = name; this.sex = sex; this.age = age; } @Override public String toString() { return "User [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + "]"; } }
创建5个对象并将其存入缓存中,以便我们进行测试
//连接redis Jedis jedis = new Jedis("127.0.0.1",6379); Map<string> map = new HashMap<string>(); final String USER_TABLE = "USER_TABLE"; //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()); String uuid2 = UUID.randomUUID().toString(); User user2 = new User(uuid2, "y2", "m", 18); map.put(uuid2, JSONObject.fromObject(user2).toString()); 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()); String uuid5 = UUID.randomUUID().toString(); User user5 = new User(uuid5, "y5", "m", 25); map.put(uuid5, JSONObject.fromObject(user5).toString()); //把map存到缓存中 jedis.hmset("USER_TABLE", map);</string></string>
在redis中查询,可以看到已经将5个user对象存到缓存中
接下来,首先实现单条件的查询,比如说查询年龄为15的user和性别为m的user
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> map = new HashMap<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);</string></string>
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); }</user></user></string>
结果如下:
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); }</user></user></string>
User [id=63a970ec-e997-43e0-8ed9-14c5eb87de8b, name=y1, sex=m, age=15]
更多redis知识请关注redis入门教程栏目。
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