Example of a Custom Condition in Kotlin

Author: jeffgbutler

src/test/kotlin/examples/kotlin/mybatis3/mariadb/KIsLikeEscape.kt

@@ -1,44 +1,54 @@
 package examples.kotlin.mybatis3.mariadb
 
+import java.util.function.Predicate
+import java.util.function.Function
 import org.mybatis.dynamic.sql.AbstractSingleValueCondition
 import org.mybatis.dynamic.sql.BindableColumn
 import org.mybatis.dynamic.sql.render.RenderingContext
 import org.mybatis.dynamic.sql.util.FragmentAndParameters
-import java.util.function.Predicate
 
-open class KIsLikeEscape<T : Any>(value: T, private val escapeCharacter: Char? = null) : AbstractSingleValueCondition<T>(value) {
+sealed class KIsLikeEscape<T : Any>(
+    value: T,
+    private val escapeCharacter: Char? = null
+) : AbstractSingleValueCondition<T>(value) {
 
     override fun operator(): String = "like"
 
     override fun renderCondition(
         renderingContext: RenderingContext,
         leftColumn: BindableColumn<T>
-    ): FragmentAndParameters {
-        val f = super.renderCondition(renderingContext, leftColumn)
-
-        return escapeCharacter?.let { f.mapFragment{ "$it ESCAPE '$escapeCharacter'"} } ?: f
+    ): FragmentAndParameters = with(super.renderCondition(renderingContext, leftColumn)) {
+        escapeCharacter?.let { mapFragment { "$it ESCAPE '$escapeCharacter'" } } ?: this
     }
 
-    override fun filter(predicate: Predicate<in T>): KIsLikeEscape<T> {
-        return filterSupport(predicate, ::empty, this)
-    }
+    override fun filter(predicate: Predicate<in T>): KIsLikeEscape<T> =
+        filterSupport(predicate, EmptyIsLikeEscape::empty, this)
 
-    fun <R : Any> map(mapper : (T) -> R): KIsLikeEscape<R> {
-        return mapSupport(mapper, { r -> KIsLikeEscape(r, escapeCharacter) }, ::empty)
+    fun <R : Any> map(mapper : Function<in T, out R>): KIsLikeEscape<R> =
+        mapSupport(mapper, { r -> ConcreteIsLikeEscape(r, escapeCharacter) }, EmptyIsLikeEscape::empty)
+
+    companion object {
+        fun <T: Any> isLike(value: T, escapeCharacter: Char? = null) : KIsLikeEscape<T> =
+            ConcreteIsLikeEscape(value, escapeCharacter)
     }
+}
+
+private class ConcreteIsLikeEscape<T: Any>(
+    value: T,
+    escapeCharacter: Char? = null
+) : KIsLikeEscape<T>(value, escapeCharacter)
 
-    private class EmptyCondition : KIsLikeEscape<Any>(-1) {
-        override fun isEmpty(): Boolean = true
+private class EmptyIsLikeEscape : KIsLikeEscape<Any>(-1) {
+    override fun isEmpty(): Boolean = true
 
-        override fun value(): Any {
-            throw NoSuchElementException("No value present") //$NON-NLS-1$
-        }
+    override fun value(): Any {
+        throw NoSuchElementException("No value present")
     }
 
     companion object {
-        private val EMPTY: KIsLikeEscape<Any> = EmptyCondition()
+        private val EMPTY: KIsLikeEscape<Any> = EmptyIsLikeEscape()
 
         @Suppress("UNCHECKED_CAST")
-        fun <T : Any> empty(): KIsLikeEscape<T> = EMPTY as KIsLikeEscape<T>
+        internal fun <T : Any> empty(): KIsLikeEscape<T> = EMPTY as KIsLikeEscape<T>
     }
 }

src/test/kotlin/examples/kotlin/mybatis3/mariadb/KMariaDBTest.kt

@@ -38,6 +38,7 @@ import org.mybatis.dynamic.sql.util.mybatis3.CommonUpdateMapper
 import org.testcontainers.containers.MariaDBContainer
 import org.testcontainers.junit.jupiter.Container
 import org.testcontainers.junit.jupiter.Testcontainers
+import java.util.*
 
 @Testcontainers
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
@@ -142,6 +143,82 @@ class KMariaDBTest {
         }
     }
 
+    @Test
+    fun testIsLikeEscape() {
+        sqlSessionFactory.openSession().use { session ->
+            val mapper = session.getMapper(CommonSelectMapper::class.java)
+            val selectStatement = select(id, description) {
+                from(items)
+                where {
+                    description(KIsLikeEscape.isLike("Item 1%", '#'))
+                }
+            }
+
+            assertThat(selectStatement.selectStatement).isEqualTo("select id, description from items where description like #{parameters.p1,jdbcType=VARCHAR} ESCAPE '#'")
+            assertThat(selectStatement.parameters).containsEntry("p1", "Item 1%")
+
+            val rows = mapper.selectManyMappedRows(selectStatement)
+            assertThat(rows).hasSize(11)
+        }
+    }
+
+    @Test
+    fun testIsLikeEscapeNoEscapeCharacter() {
+        val selectStatement = select(id, description) {
+            from(items)
+            where {
+                description(KIsLikeEscape.isLike("%fred%"))
+            }
+        }
+
+        assertThat(selectStatement.selectStatement).isEqualTo("select id, description from items where description like #{parameters.p1,jdbcType=VARCHAR}")
+        assertThat(selectStatement.parameters).containsEntry("p1", "%fred%")
+    }
+
+    @Test
+    fun testIsLikeEscapeMap() {
+        val selectStatement = select(id, description) {
+            from(items)
+            where {
+                description(KIsLikeEscape.isLike("%fred%", '#').map { s -> s.uppercase(Locale.getDefault()) })
+            }
+        }
+
+        assertThat(selectStatement.selectStatement).isEqualTo("select id, description from items where description like #{parameters.p1,jdbcType=VARCHAR} ESCAPE '#'")
+        assertThat(selectStatement.parameters).containsEntry("p1", "%FRED%")
+    }
+
+    @Test
+    fun testIsLikeEscapeFilter() {
+        val selectStatement = select(id, description) {
+            from(items)
+            where {
+                description(KIsLikeEscape.isLike("%fred%", '#').filter { _ -> false })
+            }
+            configureStatement { isNonRenderingWhereClauseAllowed = true }
+        }
+
+        assertThat(selectStatement.selectStatement).isEqualTo("select id, description from items")
+        assertThat(selectStatement.parameters).isEmpty()
+    }
+
+    @Test
+    fun testIsLikeEscapeFilterMapFilter() {
+        val selectStatement = select(id, description) {
+            from(items)
+            where {
+                description(KIsLikeEscape.isLike("%fred%", '#')
+                    .filter { _ -> true }
+                    .map { s -> s.uppercase(Locale.getDefault()) }
+                    .filter{_ -> false })
+            }
+            configureStatement { isNonRenderingWhereClauseAllowed = true }
+        }
+
+        assertThat(selectStatement.selectStatement).isEqualTo("select id, description from items")
+        assertThat(selectStatement.parameters).isEmpty()
+    }
+
     companion object {
         @Container
         private val mariadb = MariaDBContainer(TestContainersConfiguration.MARIADB_LATEST)