Support for fuction call

README.md

@@ -404,4 +404,61 @@ You must use the [ISO 8601](https://json-schema.org/understanding-json-schema/re
 >If your request conform timezone pattern, the library will use `jsonb_path_exists_tz.  
 >Then consider the timezone consideration of the [official documentation](https://www.postgresql.org/docs/current/functions-json.html)
 
+## Stored procedure 
 
+RSQL can call a stored procedure with the following syntax for both search and sort.  
+In order to be authorized to call a stored procedure, it must be `whitelisted` and not `blacklisted`.  
+The only way to whitelist or blacklist a stored procedure is to use the `QuerySupport` when performing the search or the `SortSupport` when performing the sort.
+
+```java
+String rsql = "@concat[greetings|#123]=='HELLO123'";
+QuerySupport querySupport = QuerySupport.builder()
+        .rsqlQuery(rsql)
+        .procedureWhiteList(List.of("concat", "upper"))
+        .build();
+List<Item> companies = itemRepository.findAll(toSpecification(querySupport));
+```
+
+>Regex like expression can be used to whitelist or blacklist stored procedure.
+
+### Syntax
+
+A procedure must be prefixed with `@` and called with `[]` for arguments.
+
+```
+@procedure_name[arg1|arg2|...]
+```
+
+### Arguments
+
+Arguments are separated by `|` and can be:
+* constant (null, boolean, number, string), prefixed with `#`
+* column name
+* other procedure call
+
+```
+@procedure_name[arg1|arg2|...]
+@procedure_name[column1|column2|...]
+@procedure_name[@function_name[arg1|arg2|...]|column1|#textvalue|#123|#true|#false|#null]
+```
+
+For text value, since space is not supported by RSQL, you can use `\t` to replace space.
+
+
+### Usage
+
+#### Search
+
+```java
+String rsql1 = "@upper[code]==HELLO";
+String rsql2 = "@concat[@upper[code]|name]=='TESTTest Lab'";
+String rsql3 = "@concat[@upper[code]|#123]=='HELLO123'";
+```
+
+#### Sort
+
+```java
+String sort1 = "@upper[code],asc";
+String sort2 = "@concat[@upper[code]|name],asc";
+String sort3 = "@concat[@upper[code]|#123],asc";
+```

rsql-common/src/main/java/io/github/perplexhub/rsql/FunctionBlackListedException.java

@@ -0,0 +1,8 @@
+package io.github.perplexhub.rsql;
+
+public class FunctionBlackListedException extends RSQLException {
+
+    public FunctionBlackListedException(String functionName) {
+        super(String.format("Function '%s' is blacklisted", functionName));
+    }
+}

rsql-common/src/main/java/io/github/perplexhub/rsql/FunctionNotWhiteListedException.java

@@ -0,0 +1,8 @@
+package io.github.perplexhub.rsql;
+
+public class FunctionNotWhiteListedException extends RSQLException {
+
+    public FunctionNotWhiteListedException(String functionName) {
+        super(String.format("Function '%s' is not whitelisted", functionName));
+    }
+}

rsql-common/src/main/java/io/github/perplexhub/rsql/PathUtils.java

@@ -7,6 +7,11 @@
 import java.util.Optional;
 
 public class PathUtils {
+
+    private PathUtils() {
+        throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
+    }
+
     /**
      * If the beginning of the property path is mapped, replace it with the mapped value.
      *

rsql-common/src/main/java/io/github/perplexhub/rsql/RSQLVisitorBase.java

@@ -44,10 +44,14 @@ protected Map<Class, ManagedType> getManagedTypeMap() {
 		return managedTypeMap != null ? managedTypeMap : Collections.emptyMap();
 	}
 
-	protected Map<String, EntityManager> getEntityManagerMap() {
+	public static Map<String, EntityManager> getEntityManagerMap() {
 		return entityManagerMap != null ? entityManagerMap : Collections.emptyMap();
 	}
 
+	public static Database getDatabase(EntityManager entityManager) {
+		return entityManagerDatabase.get(entityManager);
+	}
+
 	protected abstract Map<String, String> getPropertyPathMapper();
 
 	public Map<Class<?>, Map<String, String>> getPropertyRemapping() {
@@ -220,13 +224,11 @@ protected <T> boolean hasPropertyName(String property, ManagedType<T> classMetad
 	}
 
 	@SneakyThrows
-	protected Class getElementCollectionGenericType(Class type, Attribute attribute) {
+	protected static Class getElementCollectionGenericType(Class type, Attribute attribute) {
 		Member member = attribute.getJavaMember();
-		if (member instanceof Field) {
-			Field field = (Field) member;
+		if (member instanceof Field field) {
 			Type genericType = field.getGenericType();
-			if (genericType instanceof ParameterizedType) {
-				ParameterizedType rawType = (ParameterizedType) genericType;
+			if (genericType instanceof ParameterizedType rawType) {
 				Class elementCollectionClass = Class.forName(rawType.getActualTypeArguments()[0].getTypeName());
 				log.info("Map element collection generic type [{}] to [{}]", attribute.getName(), elementCollectionClass);
 				return elementCollectionClass;

rsql-jpa/src/main/java/io/github/perplexhub/rsql/QuerySupport.java

@@ -4,6 +4,8 @@
 import lombok.Data;
 
 import jakarta.persistence.criteria.JoinType;
+
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 
@@ -23,6 +25,8 @@ public class QuerySupport {
     private Map<String, JoinType> joinHints;
     private Map<Class<?>, List<String>> propertyWhitelist;
     private Map<Class<?>, List<String>> propertyBlacklist;
+    private Collection<String> procedureWhiteList;
+    private Collection<String> procedureBlackList;
 
     public static class QuerySupportBuilder {}