Added support for Java 15.

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.github.collinalpert</groupId>
     <artifactId>java2db</artifactId>
-    <version>5.5.1</version>
+    <version>5.6.0</version>
     <packaging>jar</packaging>
 
     <name>Java2DB</name>
@@ -62,19 +62,19 @@
         <dependency>
             <groupId>com.github.collinalpert</groupId>
             <artifactId>lambda2sql</artifactId>
-            <version>2.2.1</version>
+            <version>2.3.0</version>
         </dependency>
 
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
-            <version>8.0.19</version>
+            <version>8.0.22</version>
         </dependency>
 
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>
-            <version>5.6.1</version>
+            <version>5.7.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>
@@ -146,7 +146,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-assembly-plugin</artifactId>
-                <version>3.2.0</version>
+                <version>3.3.0</version>
                 <executions>
                     <execution>
                         <phase>package</phase>

src/main/java/com/github/collinalpert/java2db/annotations/ColumnName.java

@@ -1,9 +1,6 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * Sets the name of a column in a table for a POJO field.

src/main/java/com/github/collinalpert/java2db/annotations/Default.java

@@ -1,9 +1,6 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * This annotation tells Java2DB to always use the database-default for a column on create or update. Not to be confused with the {@link DefaultIfNull} annotation.

src/main/java/com/github/collinalpert/java2db/annotations/DefaultIfNull.java

@@ -1,9 +1,6 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * This annotation tells Java2DB to use the database-default for a column if the corresponding Java field marked with this annotation is {@code null}.

src/main/java/com/github/collinalpert/java2db/annotations/ForeignKeyEntity.java

@@ -1,19 +1,16 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * Marks a field as the correspondent object to a foreign key.
  * This property does not have to exist on the database.
  * Its parameter is the name of the foreign key column.
- *
+ * <p>
  * This annotation can be used on two types of objects:
  * 1) Entities which represent real objects of foreign key tables. In this case the entity has to extend
  * {@link com.github.collinalpert.java2db.entities.BaseEntity}. Because this entity represents a table it should extend {@code BaseEntity} anyway.
- *
+ * <p>
  * 2) Foreign keys to a table with static values that can be represented by an enum because they don't change.
  * In that case the enum must extend {@link com.github.collinalpert.java2db.contracts.IdentifiableEnum} and map the ids from the table.
  *

src/main/java/com/github/collinalpert/java2db/annotations/ForeignKeyPath.java

@@ -2,10 +2,7 @@
 
 import com.github.collinalpert.java2db.entities.BaseEntity;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * This annotation is used to indicate that only a specific column of a table is supposed to be joined when executing the query.

src/main/java/com/github/collinalpert/java2db/annotations/Ignore.java

@@ -1,9 +1,6 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * Marks a field as ignored, meaning it does not exist on the database or should not be filled with values.

src/main/java/com/github/collinalpert/java2db/annotations/TableName.java

@@ -1,9 +1,6 @@
 package com.github.collinalpert.java2db.annotations;
 
-import java.lang.annotation.ElementType;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.lang.annotation.Target;
+import java.lang.annotation.*;
 
 /**
  * Specifies the database table name for an entity.

src/main/java/com/github/collinalpert/java2db/database/ConnectionPool.java

@@ -0,0 +1,37 @@
+package com.github.collinalpert.java2db.database;
+
+import com.github.collinalpert.java2db.transactions.Transaction;
+
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * @author Collin Alpert
+ */
+public class ConnectionPool {
+
+	private static final Map<String, Transaction> transactions;
+	private static final DBConnection connection;
+
+	static {
+		connection = new DBConnection();
+		transactions = new ConcurrentHashMap<>();
+	}
+
+	public static DBConnection getConnection() {
+		var transactionOptional = StackWalker.getInstance().walk(s -> s.limit(10).map(x -> transactions.get(String.format("%s$%s", x.getClassName(), x.getMethodName()))).filter(Objects::nonNull).findFirst());
+		if (transactionOptional.isEmpty()) {
+			return connection;
+		}
+
+		return transactionOptional.get().getConnection();
+	}
+
+	public static void enlistTransaction(String transactionId, Transaction transaction) {
+		transactions.put(transactionId, transaction);
+	}
+
+	public static void removeTransaction(String transactionId) {
+		transactions.remove(transactionId);
+	}
+}

src/main/java/com/github/collinalpert/java2db/database/DBConnection.java

@@ -2,21 +2,14 @@
 
 import com.github.collinalpert.java2db.exceptions.ConnectionFailedException;
 import com.github.collinalpert.java2db.mappers.FieldMapper;
-import com.github.collinalpert.java2db.queries.Queryable;
-import com.github.collinalpert.java2db.queries.StoredProcedureQuery;
-import com.github.collinalpert.java2db.queries.async.AsyncQueryable;
-import com.github.collinalpert.java2db.queries.async.AsyncStoredProcedureQuery;
+import com.github.collinalpert.java2db.queries.*;
+import com.github.collinalpert.java2db.queries.async.*;
 import com.mysql.cj.exceptions.CJCommunicationsException;
 import com.mysql.cj.jdbc.exceptions.CommunicationsException;
 
 import java.io.Closeable;
-import java.sql.Connection;
-import java.sql.DriverManager;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-import java.sql.Statement;
-import java.util.Optional;
-import java.util.StringJoiner;
+import java.sql.*;
+import java.util.*;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Consumer;
 
@@ -63,7 +56,7 @@ public class DBConnection implements Closeable {
 	 */
 	public static boolean LOG_QUERIES = true;
 
-	private Connection connection;
+	private Connection underlyingConnection;
 	private boolean isConnectionValid;
 
 	public DBConnection() {
@@ -73,7 +66,7 @@ public DBConnection() {
 			System.setProperty("user", USERNAME);
 			System.setProperty("password", PASSWORD);
 			DriverManager.setLoginTimeout(TIMEOUT);
-			connection = DriverManager.getConnection(connectionString, System.getProperties());
+			underlyingConnection = DriverManager.getConnection(connectionString, System.getProperties());
 			isConnectionValid = true;
 		} catch (CJCommunicationsException | CommunicationsException e) {
 			isConnectionValid = false;
@@ -84,6 +77,11 @@ public DBConnection() {
 		}
 	}
 
+	public DBConnection(Connection underlyingConnection) {
+		this.underlyingConnection = underlyingConnection;
+		this.isConnectionValid = true;
+	}
+
 	/**
 	 * Checks if the connection is valid/successful.
 	 *
@@ -102,7 +100,7 @@ public boolean isValid() {
 	 * @throws SQLException if the query is malformed or cannot be executed.
 	 */
 	public ResultSet execute(String query) throws SQLException {
-		var statement = this.connection.createStatement();
+		var statement = this.underlyingConnection.createStatement();
 		log(query);
 		var set = statement.executeQuery(query);
 		statement.closeOnCompletion();
@@ -119,7 +117,7 @@ public ResultSet execute(String query) throws SQLException {
 	 * @throws SQLException if the query is malformed or cannot be executed.
 	 */
 	public ResultSet execute(String query, Object... params) throws SQLException {
-		var statement = this.connection.prepareStatement(query);
+		var statement = this.underlyingConnection.prepareStatement(query);
 		for (int i = 0; i < params.length; i++) {
 			statement.setObject(i + 1, params[i]);
 		}
@@ -138,7 +136,7 @@ public ResultSet execute(String query, Object... params) throws SQLException {
 	 * @throws SQLException if the query is malformed or cannot be executed.
 	 */
 	public long update(String query) throws SQLException {
-		var statement = this.connection.createStatement();
+		var statement = this.underlyingConnection.createStatement();
 		log(query);
 		statement.executeUpdate(query, Statement.RETURN_GENERATED_KEYS);
 		return updateInternal(statement);
@@ -153,7 +151,7 @@ public long update(String query) throws SQLException {
 	 * @throws SQLException if the query is malformed or cannot be executed.
 	 */
 	public long update(String query, Object... params) throws SQLException {
-		var statement = this.connection.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
+		var statement = this.underlyingConnection.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
 		for (int i = 0; i < params.length; i++) {
 			statement.setObject(i + 1, params[i]);
 		}
@@ -171,7 +169,7 @@ public long update(String query, Object... params) throws SQLException {
 	 */
 	public boolean isOpen() {
 		try {
-			return !this.connection.isClosed();
+			return !this.underlyingConnection.isClosed();
 		} catch (SQLException e) {
 			System.err.println("Could not determine connection status");
 			return this.isConnectionValid = false;
@@ -184,8 +182,8 @@ public boolean isOpen() {
 	@Override
 	public void close() {
 		try {
-			if (this.connection != null) {
-				this.connection.close();
+			if (this.underlyingConnection != null) {
+				this.underlyingConnection.close();
 			}
 		} catch (SQLException e) {
 			System.err.println("Could not close database connection");
@@ -195,6 +193,16 @@ public void close() {
 		}
 	}
 
+	/**
+	 * Calls an SQL function.
+	 *
+	 * @param returnType   The Java equivalent of the SQL datatype the function returns.
+	 * @param functionName The name of the function.
+	 * @param arguments    The arguments to be supplied to the function.
+	 * @param <T>          The functions return type.
+	 * @return The value of the function, as a Java datatype.
+	 * @throws SQLException In case there is an error communicating with the database, i.e. the function does not exist.
+	 */
 	public <T> Optional<T> callFunction(Class<T> returnType, String functionName, Object... arguments) throws SQLException {
 		var joiner = new StringJoiner(",");
 		for (int i = 0; i < arguments.length; i++) {
@@ -210,6 +218,10 @@ public <T> CompletableFuture<Optional<T>> callFunctionAsync(Consumer<SQLExceptio
 		return CompletableFuture.supplyAsync(supplierHandling(() -> this.callFunction(returnType, functionName, arguments), exceptionHandler));
 	}
 
+	public <T> CompletableFuture<Void> callFunctionAsync(Consumer<SQLException> exceptionHandler, Consumer<? super Optional<T>> callback, Class<T> returnType, String functionName, Object... arguments) {
+		return CompletableFuture.supplyAsync(supplierHandling(() -> this.callFunction(returnType, functionName, arguments), exceptionHandler)).thenAcceptAsync(callback);
+	}
+
 	public <T> Queryable<T> callStoredProcedure(Class<T> returnType, String storedProcedureName, Object... arguments) {
 		return new StoredProcedureQuery<>(returnType, this, storedProcedureName, arguments);
 	}
@@ -218,6 +230,10 @@ public <T> AsyncQueryable<T> callStoredProcedureAsync(Class<T> returnType, Strin
 		return new AsyncStoredProcedureQuery<>(returnType, this, storedProcedureName, arguments);
 	}
 
+	public Connection underlyingConnection() {
+		return this.underlyingConnection;
+	}
+
 	/**
 	 * Prints queries to the console, while considering the {@link DBConnection#LOG_QUERIES} constant.
 	 *