From 19f572f53be001976ac9f805c494c204aa638a94 Mon Sep 17 00:00:00 2001
From: berry120 <berry120@gmail.com>
Date: Mon, 2 Sep 2019 17:19:39 +0100
Subject: [PATCH] #166 - Add the ability to define dialect-specific converters
 in R2dbcDialect for MySQL.

Add a MySql specific dialect converter for converting from byte to boolean.

Original pull request: #168.
---
 .../config/AbstractR2dbcConfiguration.java    |  2 +-
 .../data/r2dbc/dialect/MySqlDialect.java      | 46 +++++++++++++++++++
 .../data/r2dbc/dialect/R2dbcDialect.java      |  9 ++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/springframework/data/r2dbc/config/AbstractR2dbcConfiguration.java b/src/main/java/org/springframework/data/r2dbc/config/AbstractR2dbcConfiguration.java
index 6b1d1bbb..8e1ea709 100644
--- a/src/main/java/org/springframework/data/r2dbc/config/AbstractR2dbcConfiguration.java
+++ b/src/main/java/org/springframework/data/r2dbc/config/AbstractR2dbcConfiguration.java
@@ -174,7 +174,7 @@ public abstract class AbstractR2dbcConfiguration implements ApplicationContextAw
 	protected StoreConversions getStoreConversions() {
 
 		R2dbcDialect dialect = getDialect(lookupConnectionFactory());
-		return StoreConversions.of(dialect.getSimpleTypeHolder(), R2dbcCustomConversions.STORE_CONVERTERS);
+		return StoreConversions.of(dialect.getSimpleTypeHolder(), dialect.getConverters(), R2dbcCustomConversions.STORE_CONVERTERS);
 	}
 
 	/**
diff --git a/src/main/java/org/springframework/data/r2dbc/dialect/MySqlDialect.java b/src/main/java/org/springframework/data/r2dbc/dialect/MySqlDialect.java
index 78f2c015..3259e9ea 100644
--- a/src/main/java/org/springframework/data/r2dbc/dialect/MySqlDialect.java
+++ b/src/main/java/org/springframework/data/r2dbc/dialect/MySqlDialect.java
@@ -18,11 +18,15 @@ package org.springframework.data.r2dbc.dialect;
 import java.net.InetAddress;
 import java.net.URI;
 import java.net.URL;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.UUID;
+import org.springframework.core.convert.converter.Converter;
 
 /**
  * An SQL dialect for MySQL.
@@ -41,6 +45,19 @@ public class MySqlDialect extends org.springframework.data.relational.core.diale
 	public static final MySqlDialect INSTANCE = new MySqlDialect();
 
 	private static final BindMarkersFactory ANONYMOUS = BindMarkersFactory.anonymous("?");
+	
+	/**
+	 * MySql specific converters.
+	 */
+	public static final List<Object> CONVERTERS;
+	
+	static {
+		List<Object> converters = new ArrayList<>();
+
+		converters.add(ByteToBooleanConverter.INSTANCE);
+
+		CONVERTERS = Collections.unmodifiableList(converters);
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -59,4 +76,33 @@ public class MySqlDialect extends org.springframework.data.relational.core.diale
 	public Collection<? extends Class<?>> getSimpleTypes() {
 		return SIMPLE_TYPES;
 	}
+	
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.r2dbc.dialect.R2dbcDialect#getConverters()
+	 */
+	@Override
+	public Collection<Object> getConverters() {
+		return CONVERTERS;
+	}
+        
+	/**
+	 * Simple singleton to convert {@link Byte}s to their {@link Boolean}
+	 * representation. MySQL does not have a built in boolean type by default,
+	 * so relies on using a byte instead. Non-zero values represent true.
+	 *
+	 * @author Michael Berry
+	 */
+	public enum ByteToBooleanConverter implements Converter<Byte, Boolean> {
+
+		INSTANCE;
+
+		@Override
+		public Boolean convert(Byte s) {
+			if (s == null) {
+				return null;
+			}
+			return s != 0;
+		}
+	}
 }
diff --git a/src/main/java/org/springframework/data/r2dbc/dialect/R2dbcDialect.java b/src/main/java/org/springframework/data/r2dbc/dialect/R2dbcDialect.java
index 510fb7fa..b1b420d3 100644
--- a/src/main/java/org/springframework/data/r2dbc/dialect/R2dbcDialect.java
+++ b/src/main/java/org/springframework/data/r2dbc/dialect/R2dbcDialect.java
@@ -48,4 +48,13 @@ public interface R2dbcDialect extends Dialect {
 
 		return new SimpleTypeHolder(simpleTypes, true);
 	}
+
+	/**
+	 * Return a collection of converters for this dialect.
+	 * 
+	 * @return a collection of converters for this dialect.
+	 */
+	default Collection<Object> getConverters() {
+		return Collections.emptySet();
+	}
 }