JarCasting
jedis-utils
Utilities for common tasks using Jedis (the java redis client).
Jedis Collections
An abstraction of Redis' value types by implementing java.util collection interfaces.
Includes:
| Jedis Collection | Corresponding java.util Interface |
Redis Type | Comments |
|---|---|---|---|
JedisMap |
Map |
hash |
|
JedisList |
List |
list |
Implements java.util.Collection, not java.util.List, because of a random access limitation, but gives an ordered collection functionality, close enough to a list |
JedisSet |
Set |
set |
|
JedisSortedSet |
Set |
zset |
In order to "wrap" a Redis value with the appropriate abstraction, use the JedisCollections facade. For example, in order to wrap the hash value in the myhash key in database index 2, use:
JedisPool jedisPool = getJedisPool();
JedisCollections jedisCollections = new JedisCollections(jedisPool);
Map<String, String> myhash = jedisCollections.getMap(2, "myhash");
The method above (using a JedisPool) is the preferred way to create a wrapper. In addition, you can use JedisCollections' static methods, but then you are responsible for managing the provided Jedis instance and keeping it pointing to the correct database index. For example:
Jedis jedis = getJedis();
jedis.select(2);
Set<String> myset = JedisCollections.getSet(jedis, "myset");
Jedis Keys Scanner
The JedisKeysScanner is an iterator which scans for keys in a redis database. This implementation is based on the SCAN redis command. Similar to the collections, a keys scanner can use either a JedisPool (preferred) or a Jedis instance.
JedisKeysScanner scanner = new JedisKeysScanner(jedisPool, 0);
while (scanner.hasNext()) {
String key = scanner.next();
//do something...
}
A scan can be limitted by pattern and count using the jedis ScanParams.
JedisKeysScanner scanner = new JedisKeysScanner(jedis, new ScanParams().match("my_prefix*"));
while (scanner.hasNext()) {
String key = scanner.next();
//Only keys which start with "my_prefix"
}
Lua Script Builder
A builder facility for building lua scripts to be executed in Redis using Jedis. The builder uses an API similar to the API provided by Jedis.
For example:
import static org.yatech.jedis.utils.lua.LuaScriptBuilder.*;
import org.yatech.jedis.utils.lua.LuaScriptBuilder;
import org.yatech.jedis.utils.lua.LuaScript;
import org.yatech.jedis.utils.lua.LuaLocalArray;
...
LuaScriptBuilder builder = startScript();
builder.select(0);
LuaLocalArray data = builder.hgetAll("key1");
builder.select(1);
.hmset("key1", data)
.select(0)
.del("key1");
LuaScript script = builder.endScript();
Jedis jedis = ...
script.exec(jedis);
It is also possible to create prepared scripts with arguments and with some control statements. For example (this time in Groovy):
import static org.yatech.jedis.utils.lua.LuaScriptBuilder.*
import static org.yatech.jedis.utils.lua.LuaConditoins.*
...
def key1 = newKeyArgument('key1')
def key2 = newKeyArgument('key2')
def member = newStringValueArgument('member')
def score = newDoubleValueArgument('score')
def db0 = newIntValueArgument('db0')
def db1 = newIntValueArgument('db1')
def script = startScript().with {
select(db0)
def payload = hgetAll(key1)
select(db1)
def existingScore = zscore(key2, member)
ifCondition(isNull(existingScore)).then(startBlock(it).with {
zadd(key2, score, member)
endBlock()
}).endIf()
hmset(key1, payload)
select(db0)
del(key1)
endPreparedScript()
}
script.setKeyArgument('key1','myhash1')
script.setKeyArgument('key2','myzset1')
script.setValueArgument('db0',7)
script.setValueArgument('db1',8)
script.setValueArgument('member','thefirstmember')
script.setValueArgument('score',1.234)
Jedis jedis = ...
script.exec(jedis)
Thread-safe Lua Prepared Script
If you need to have a prepared lua script which should be used in a multithreaded application, it is advised to create it as thread-safe. In order to do so, use LuaScriptConfig and set threadSafe to true. See example below:
import org.yatech.jedis.utils.lua.LuaPreparedScript;
import org.yatech.jedis.utils.lua.LuaScriptConfig;
import org.yatech.jedis.utils.lua.LuaValue;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import static org.yatech.jedis.utils.lua.LuaScriptBuilder.*;
public class MyService {
private final LuaPreparedScript script;
private final JedisPool jedisPool;
public MyService() {
this.script = createScript();
this.jedisPool = new JedisPool();
}
private LuaPreparedScript createScript() {
LuaValue<String> zsetKey = newKeyArgument("zset_key");
LuaValue<Double> score = newDoubleValueArgument("score");
LuaValue<String> member = newStringValueArgument("member");
LuaScriptConfig config = LuaScriptConfig.newConfig().threadSafe(true).build();
LuaPreparedScript script = startScript()
.zadd(zsetKey, score, member)
.endPreparedScript(config);
return script;
}
public void addMember(String member, double score) {
script.setKeyArgument("zset_key", "ordered_members");
script.setValueArgument("member", member);
script.setValueArgument("score", score);
try (Jedis jedis = jedisPool.getResource()) {
script.exec(jedis);
}
}
public void destroy() {
jedisPool.destroy();
}
}
Script Caching
Script caching is enabled by default and is handled internally. This reduces the need to load the script to redis each time it is executed. If you prefer not to use script caching for any reason, use LuaScriptConfig and set useScriptCaching to false:
LuaScriptConfig config = LuaScriptConfig.newConfig().useScriptCaching(false).build();
Assign Value to an Existing Local Variable
In order to reuse an existing local variable, use the assign builder method:
LuaScriptBuilder builder = startScript();
LuaLocalValue myLocal = builder.get("mykey1");
LuaScript script = builder
.set("mykey2", myLocal)
.assign(myLocal, builder.get("mykey3"))
.endScriptReturn(myLocal);
