redis怎么实现条件查询？

Redis怎么实现条件查询？这个问题可能是我们日常工作经常见到的。通过这个问题，希望你能收获更多。今天跟随小编一起来看解决方案吧。

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, String> map = new HashMap<String,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);

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, 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:

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 [id=63a970ec-e997-43e0-8ed9-14c5eb87de8b, name=y1, sex=m, age=15]

以上就是redis实现条件查询的方法介绍，代码示例简单明了，如果在日常工作遇到此问题。通过这篇文章，希望你能有所收获，更多详情敬请关注编程网数据库频道！