DataClassRowMapper exposes generic constructor parameters for type conversion

Closes gh-26881

Author: jhoeller

spring-jdbc/src/main/java/org/springframework/jdbc/core/DataClassRowMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -22,7 +22,9 @@
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.TypeConverter;
+import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -50,7 +52,7 @@ public class DataClassRowMapper<T> extends BeanPropertyRowMapper<T> {
 	private String[] constructorParameterNames;
 
 	@Nullable
-	private Class<?>[] constructorParameterTypes;
+	private TypeDescriptor[] constructorParameterTypes;
 
 
 	/**
@@ -75,9 +77,13 @@ protected void initialize(Class<T> mappedClass) {
 		super.initialize(mappedClass);
 
 		this.mappedConstructor = BeanUtils.getResolvableConstructor(mappedClass);
-		if (this.mappedConstructor.getParameterCount() > 0) {
+		int paramCount = this.mappedConstructor.getParameterCount();
+		if (paramCount > 0) {
 			this.constructorParameterNames = BeanUtils.getParameterNames(this.mappedConstructor);
-			this.constructorParameterTypes = this.mappedConstructor.getParameterTypes();
+			this.constructorParameterTypes = new TypeDescriptor[paramCount];
+			for (int i = 0; i < paramCount; i++) {
+				this.constructorParameterTypes[i] = new TypeDescriptor(new MethodParameter(this.mappedConstructor, i));
+			}
 		}
 	}
 
@@ -90,8 +96,9 @@ protected T constructMappedInstance(ResultSet rs, TypeConverter tc) throws SQLEx
 			args = new Object[this.constructorParameterNames.length];
 			for (int i = 0; i < args.length; i++) {
 				String name = underscoreName(this.constructorParameterNames[i]);
-				Class<?> type = this.constructorParameterTypes[i];
-				args[i] = tc.convertIfNecessary(getColumnValue(rs, rs.findColumn(name), type), type);
+				TypeDescriptor td = this.constructorParameterTypes[i];
+				Object value = getColumnValue(rs, rs.findColumn(name), td.getType());
+				args[i] = tc.convertIfNecessary(value, td.getType(), td);
 			}
 		}
 		else {

spring-jdbc/src/test/java/org/springframework/jdbc/core/AbstractRowMapperTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -135,6 +135,7 @@ public Mock(MockType type) throws Exception {
 			given(resultSet.getObject(anyInt(), any(Class.class))).willThrow(new SQLFeatureNotSupportedException());
 			given(resultSet.getDate(3)).willReturn(new java.sql.Date(1221222L));
 			given(resultSet.getBigDecimal(4)).willReturn(new BigDecimal("1234.56"));
+			given(resultSet.getObject(4)).willReturn(new BigDecimal("1234.56"));
 			given(resultSet.wasNull()).willReturn(type == MockType.TWO);
 
 			given(resultSetMetaData.getColumnCount()).willReturn(4);

spring-jdbc/src/test/java/org/springframework/jdbc/core/DataClassRowMapperTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,11 +16,15 @@
 
 package org.springframework.jdbc.core;
 
+import java.math.BigDecimal;
+import java.util.Collections;
+import java.util.Date;
 import java.util.List;
 
 import org.junit.jupiter.api.Test;
 
 import org.springframework.jdbc.core.test.ConstructorPerson;
+import org.springframework.jdbc.core.test.ConstructorPersonWithGenerics;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -42,4 +46,20 @@ public void testStaticQueryWithDataClass() throws Exception {
 		mock.verifyClosed();
 	}
 
+	@Test
+	public void testStaticQueryWithDataClassAndGenerics() throws Exception {
+		Mock mock = new Mock();
+		List<ConstructorPersonWithGenerics> result = mock.getJdbcTemplate().query(
+				"select name, age, birth_date, balance from people",
+				new DataClassRowMapper<>(ConstructorPersonWithGenerics.class));
+		assertThat(result.size()).isEqualTo(1);
+		ConstructorPersonWithGenerics person = result.get(0);
+		assertThat(person.name()).isEqualTo("Bubba");
+		assertThat(person.age()).isEqualTo(22L);
+		assertThat(person.birth_date()).usingComparator(Date::compareTo).isEqualTo(new java.util.Date(1221222L));
+		assertThat(person.balance()).isEqualTo(Collections.singletonList(new BigDecimal("1234.56")));
+
+		mock.verifyClosed();
+	}
+
 }

spring-jdbc/src/test/java/org/springframework/jdbc/core/test/ConstructorPerson.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -24,13 +24,13 @@
  */
 public class ConstructorPerson {
 
-	private String name;
+	private final String name;
 
-	private long age;
+	private final long age;
 
-	private java.util.Date birth_date;
+	private final Date birth_date;
 
-	private BigDecimal balance;
+	private final BigDecimal balance;
 
 
 	public ConstructorPerson(String name, long age, Date birth_date, BigDecimal balance) {
@@ -42,19 +42,19 @@ public ConstructorPerson(String name, long age, Date birth_date, BigDecimal bala
 
 
 	public String name() {
-		return name;
+		return this.name;
 	}
 
 	public long age() {
-		return age;
+		return this.age;
 	}
 
 	public Date birth_date() {
-		return birth_date;
+		return this.birth_date;
 	}
 
 	public BigDecimal balance() {
-		return balance;
+		return this.balance;
 	}
 
 }

spring-jdbc/src/test/java/org/springframework/jdbc/core/test/ConstructorPersonWithGenerics.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2002-2021 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
+ *
+ *      https://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.jdbc.core.test;
+
+import java.math.BigDecimal;
+import java.util.Date;
+import java.util.List;
+
+/**
+ * @author Juergen Hoeller
+ */
+public class ConstructorPersonWithGenerics {
+
+	private final String name;
+
+	private final long age;
+
+	private final Date birth_date;
+
+	private final List<BigDecimal> balance;
+
+
+	public ConstructorPersonWithGenerics(String name, long age, Date birth_date, List<BigDecimal> balance) {
+		this.name = name;
+		this.age = age;
+		this.birth_date = birth_date;
+		this.balance = balance;
+	}
+
+
+	public String name() {
+		return this.name;
+	}
+
+	public long age() {
+		return this.age;
+	}
+
+	public Date birth_date() {
+		return this.birth_date;
+	}
+
+	public List<BigDecimal> balance() {
+		return this.balance;
+	}
+
+}