redis implements simple conditional query

1. Import the jar package

2. Implement a simple conditional query

Create a User entity class

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 + "]";
    }
}

Create 5 objects and store them in the cache for us to test

	//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);

Query in redis, you can see that 5 user objects have been stored in the cache

Next, first implement a single-condition query, for example, query a user with an age of 15 and a user with a gender of m

Since Redis is nosql, it cannot be directly Like mysql, where is used to perform conditional queries, so if Redis wants to implement conditional queries, it can only use a stupid method: save all users who meet the conditions into a set.

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);

So, if you want to query the user whose age is 15, you need to first remove all uuid from USER_TABLE_AGE_15, and then remove the user from USER_TABLE

	//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);
	}

The results are as follows:

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]

So if you need a user with age 15 and gender m, it is very simple. Get the union of
USER_TABLE_AGE_15 and USER_TABLE_SEX_m, and then get it from USER_TABLE.

//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]

For more redis knowledge, please pay attention to the redis introductory tutorial column.

The above is the detailed content of redis implements simple conditional query. For more information, please follow other related articles on the PHP Chinese website!