DATAJDBC-278 - Add MySQL dialect.

Author: mp911de

spring-data-relational/src/main/java/org/springframework/data/relational/core/dialect/Dialect.java

@@ -18,7 +18,9 @@
 import org.springframework.data.relational.core.sql.render.SelectRenderContext;
 
 /**
- * Represents a dialect that is implemented by a particular database.
+ * Represents a dialect that is implemented by a particular database. Please note that not all features are supported by
+ * all vendors. Dialects typically express this with feature flags. Methods for unsupported functionality may throw
+ * {@link UnsupportedOperationException}.
  *
  * @author Mark Paluch
  * @author Jens Schauder
@@ -42,5 +44,10 @@ default ArrayColumns getArraySupport() {
 		return ArrayColumns.Unsupported.INSTANCE;
 	}
 
+	/**
+	 * Obtain the {@link SelectRenderContext}.
+	 *
+	 * @return the {@link SelectRenderContext}.
+	 */
 	SelectRenderContext getSelectContext();
 }

spring-data-relational/src/main/java/org/springframework/data/relational/core/dialect/MySqlDialect.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.dialect;
+
+/**
+ * An SQL dialect for MySQL.
+ *
+ * @author Mark Paluch
+ * @since 1.1
+ */
+public class MySqlDialect extends AbstractDialect {
+
+	/**
+	 * Singleton instance.
+	 */
+	public static final MySqlDialect INSTANCE = new MySqlDialect();
+
+	private static final LimitClause LIMIT_CLAUSE = new LimitClause() {
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.relational.core.dialect.LimitClause#getLimit(long)
+		 */
+		@Override
+		public String getLimit(long limit) {
+			return "LIMIT " + limit;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.relational.core.dialect.LimitClause#getOffset(long)
+		 */
+		@Override
+		public String getOffset(long offset) {
+			throw new UnsupportedOperationException("MySQL does not support OFFSET without LIMIT");
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.relational.core.dialect.LimitClause#getClause(long, long)
+		 */
+		@Override
+		public String getLimitOffset(long limit, long offset) {
+
+			// LIMIT {[offset,] row_count}
+			return String.format("LIMIT %d, %d", offset, limit);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.relational.core.dialect.LimitClause#getClausePosition()
+		 */
+		@Override
+		public Position getClausePosition() {
+			return Position.AFTER_ORDER_BY;
+		}
+	};
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.relational.core.dialect.Dialect#limit()
+	 */
+	@Override
+	public LimitClause limit() {
+		return LIMIT_CLAUSE;
+	}
+}

spring-data-relational/src/test/java/org/springframework/data/relational/core/dialect/MySqlDialectRenderingTests.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.dialect;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.data.relational.core.sql.Select;
+import org.springframework.data.relational.core.sql.StatementBuilder;
+import org.springframework.data.relational.core.sql.Table;
+import org.springframework.data.relational.core.sql.render.NamingStrategies;
+import org.springframework.data.relational.core.sql.render.SqlRenderer;
+
+/**
+ * Tests for {@link MySqlDialect}-specific rendering.
+ *
+ * @author Mark Paluch
+ */
+public class MySqlDialectRenderingTests {
+
+	private final RenderContextFactory factory = new RenderContextFactory(MySqlDialect.INSTANCE);
+
+	@Before
+	public void before() {
+		factory.setNamingStrategy(NamingStrategies.asIs());
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderSelectWithLimit() {
+
+		Table table = Table.create("foo");
+		Select select = StatementBuilder.select(table.asterisk()).from(table).limit(10).build();
+
+		String sql = SqlRenderer.create(factory.createRenderContext()).render(select);
+
+		assertThat(sql).isEqualTo("SELECT foo.* FROM foo LIMIT 10");
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderSelectWithOffset() {
+
+		Table table = Table.create("foo");
+		Select select = StatementBuilder.select(table.asterisk()).from(table).offset(10).build();
+
+		assertThatThrownBy(() -> SqlRenderer.create(factory.createRenderContext()).render(select))
+				.isInstanceOf(UnsupportedOperationException.class);
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderSelectWithLimitOffset() {
+
+		Table table = Table.create("foo");
+		Select select = StatementBuilder.select(table.asterisk()).from(table).limit(10).offset(20).build();
+
+		String sql = SqlRenderer.create(factory.createRenderContext()).render(select);
+
+		assertThat(sql).isEqualTo("SELECT foo.* FROM foo LIMIT 20, 10");
+	}
+}

spring-data-relational/src/test/java/org/springframework/data/relational/core/dialect/MySqlDialectUnitTests.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.dialect;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for {@link MySqlDialect}.
+ *
+ * @author Mark Paluch
+ */
+public class MySqlDialectUnitTests {
+
+	@Test // DATAJDBC-278
+	public void shouldNotSupportArrays() {
+
+		ArrayColumns arrayColumns = MySqlDialect.INSTANCE.getArraySupport();
+
+		assertThat(arrayColumns.isSupported()).isFalse();
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderLimit() {
+
+		LimitClause limit = MySqlDialect.INSTANCE.limit();
+
+		assertThat(limit.getClausePosition()).isEqualTo(LimitClause.Position.AFTER_ORDER_BY);
+		assertThat(limit.getLimit(10)).isEqualTo("LIMIT 10");
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderOffset() {
+
+		LimitClause limit = MySqlDialect.INSTANCE.limit();
+
+		assertThatThrownBy(() -> limit.getOffset(10)).isInstanceOf(UnsupportedOperationException.class);
+	}
+
+	@Test // DATAJDBC-278
+	public void shouldRenderLimitOffset() {
+
+		LimitClause limit = MySqlDialect.INSTANCE.limit();
+
+		assertThat(limit.getLimitOffset(20, 10)).isEqualTo("LIMIT 10, 20");
+	}
+}