[spring-jdbc-col-count] resolving runtime error when using queryForList() (#18596)

Author: sk1418

persistence-modules/spring-jdbc-2/src/main/java/com/baeldung/spring/jdbc/queryforlist/QueryForListDemoApplication.java

@@ -0,0 +1,7 @@
+package com.baeldung.spring.jdbc.queryforlist;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class QueryForListDemoApplication {
+}

persistence-modules/spring-jdbc-2/src/main/resources/com/baeldung/spring/jdbc/queryforlist/init-student-data.sql

@@ -0,0 +1,11 @@
+CREATE TABLE STUDENT_TBL
+(
+    ID    int NOT NULL PRIMARY KEY,
+    NAME  varchar(255),
+    MAJOR varchar(255)
+);
+
+INSERT INTO STUDENT_TBL VALUES (1, 'Kai', 'Computer Science');
+INSERT INTO STUDENT_TBL VALUES (2, 'Eric', 'Computer Science');
+INSERT INTO STUDENT_TBL VALUES (3, 'Kevin', 'Banking');
+INSERT INTO STUDENT_TBL VALUES (4, 'Liam', 'Law');

persistence-modules/spring-jdbc-2/src/test/java/com/baeldung/spring/jdbc/queryforlist/JdbcTemplateIntegrationTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.spring.jdbc.queryforlist;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
+import org.springframework.jdbc.IncorrectResultSetColumnCountException;
+import org.springframework.jdbc.core.BeanPropertyRowMapper;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.test.context.jdbc.Sql;
+
+@JdbcTest
+@Sql(value = { "init-student-data.sql" }, executionPhase = Sql.ExecutionPhase.BEFORE_TEST_CLASS)
+class JdbcTemplateIntegrationTest {
+
+    @Autowired
+    private JdbcTemplate jdbcTemplate;
+
+    @Test
+    void whenUsingQueryForListToGetStudentList_thenGotException() {
+        assertThrows(IncorrectResultSetColumnCountException.class, () -> jdbcTemplate.queryForList("SELECT * FROM STUDENT_TBL", Student.class));
+    }
+
+    @Test
+    void whenUsingQueryForListToSingleColumn_thenCorrect() {
+        List<String> names = jdbcTemplate.queryForList("SELECT NAME FROM STUDENT_TBL", String.class);
+        assertEquals(List.of("Kai", "Eric", "Kevin", "Liam"), names);
+
+        List<Integer> ids = jdbcTemplate.queryForList("SELECT ID FROM STUDENT_TBL", Integer.class);
+        assertEquals(List.of(1, 2, 3, 4), ids);
+    }
+
+    @Test
+    void whenUsingQueryForListToGetMap_thenCorrect() {
+        List<Map<String, Object>> nameMajorRowMaps = jdbcTemplate.queryForList("SELECT NAME, MAJOR FROM STUDENT_TBL");
+
+        // @formatter:off
+        assertEquals(List.of(
+          Map.of("NAME", "Kai", "MAJOR", "Computer Science"),
+          Map.of("NAME", "Eric", "MAJOR", "Computer Science"),
+          Map.of("NAME", "Kevin", "MAJOR", "Banking"),
+          Map.of("NAME", "Liam", "MAJOR", "Law")
+        ), nameMajorRowMaps);
+        // @formatter:on
+
+        List<Map<String, Object>> rowMaps = jdbcTemplate.queryForList("SELECT * FROM STUDENT_TBL");
+
+        // @formatter:off
+        assertEquals(List.of(
+          Map.of("ID", 1, "NAME", "Kai", "MAJOR", "Computer Science"),
+          Map.of("ID", 2, "NAME", "Eric", "MAJOR", "Computer Science"),
+          Map.of("ID", 3, "NAME", "Kevin", "MAJOR", "Banking"),
+          Map.of("ID", 4, "NAME", "Liam", "MAJOR", "Law")
+        ), rowMaps);
+        // @formatter:on
+    }
+
+    @Test
+    void whenUsingQueryWithRowMapperToGetStudentList_thenCorrect() {
+        // @formatter:off
+        List<Student> expected = List.of(
+          new Student(1, "Kai", "Computer Science"),
+          new Student(2, "Eric", "Computer Science"),
+          new Student(3, "Kevin", "Banking"),
+          new Student(4, "Liam", "Law")
+        );
+        // @formatter:on
+
+        List<Student> students = jdbcTemplate.query("SELECT * FROM STUDENT_TBL", new BeanPropertyRowMapper<>(Student.class));
+
+        assertEquals(expected, students);
+    }
+
+}

persistence-modules/spring-jdbc-2/src/test/java/com/baeldung/spring/jdbc/queryforlist/Student.java

@@ -0,0 +1,58 @@
+package com.baeldung.spring.jdbc.queryforlist;
+
+import java.util.Objects;
+
+public class Student {
+
+    private Integer id;
+    private String name;
+    private String major;
+
+    public Student() {
+    }
+
+    public Student(Integer id, String name, String major) {
+        this.id = id;
+        this.name = name;
+        this.major = major;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (!(o instanceof Student student)) {
+            return false;
+        }
+        return Objects.equals(id, student.id) && Objects.equals(name, student.name) && Objects.equals(major, student.major);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, name, major);
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getMajor() {
+        return major;
+    }
+
+    public void setMajor(String major) {
+        this.major = major;
+    }
+
+
+}