Spring JdbcTemplate RowMapper Junit Test Example

This example shows how to write junit to test Spring RowMapper functionality while mocking JdbcTemplate with Mockito.

This also increases code coverage of RowMapper code.

Below is the DAO class that returns list of users with RowMapper using Lambdas.

Spring JdbcTemplate RowMapper Example with Lambdas

package com.kswaughs.dao;

import java.sql.ResultSet;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import com.kswaughs.beans.User;

@Repository
public class UserDAO {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    public List<User> getAllUsers() {

        return jdbcTemplate.query("SELECT ID, NAME, STATUS FROM USER", 
            
            (ResultSet rs, int rowNum) -> {

                User user = new User();

                user.setId(rs.getInt("ID"));
                user.setName(rs.getString("NAME"));
                user.setStatus(rs.getBoolean("STATUS"));

                return user;
            });
        }
    }

Below is the Junit test class to test RowMapper code by mocking JdbcTemplate to return two rows.

Spring JdbcTemplate RowMapper Junit test example

package com.kswaughs.dao;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentMatchers;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.junit.MockitoJUnitRunner;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

import com.kswaughs.beans.User;

@RunWith(MockitoJUnitRunner.class)
public class UserDAOTest {

    @Mock
    private JdbcTemplate jdbcTemplate;

    @InjectMocks
    private UserDAO userDAO;

    @SuppressWarnings("unchecked")
    @Test
    public void testGetAllUsers() {

        Mockito.when(jdbcTemplate.query(
            ArgumentMatchers.anyString(), ArgumentMatchers.any(RowMapper.class)))
            .thenAnswer((invocation) -> {

                RowMapper<User> rowMapper = (RowMapper<User>) invocation.getArgument(1);
                ResultSet rs = Mockito.mock(ResultSet.class);

                // Mock ResultSet to return two rows.
                Mockito.when(rs.getInt(ArgumentMatchers.eq("ID")))
                    .thenReturn(506, 400);
                Mockito.when(rs.getString(ArgumentMatchers.eq("NAME")))
                    .thenReturn("Jim Carrey", "John Travolta");
                Mockito.when(rs.getBoolean(ArgumentMatchers.eq("STATUS")))
                    .thenReturn(true, false);

                List<User> users = new ArrayList<>();
                users.add(rowMapper.mapRow(rs, 0));
                users.add(rowMapper.mapRow(rs, 1));

                return users;
        });

        List<User> users = userDAO.getAllUsers();
        
        // Assert First Row
        assertFirstUser(users.get(0));

        // Assert Second Row
        assertSecondUser(users.get(1));
    }

    public void assertFirstUser(User user) {
        Assert.assertEquals(Integer.valueOf(506), user.getId());
        Assert.assertEquals("Jim Carrey", user.getName());
        Assert.assertTrue(user.isStatus());
    }
    
    public void assertSecondUser(User user) {
        Assert.assertEquals(Integer.valueOf(400), user.getId());
        Assert.assertEquals("John Travolta", user.getName());
        Assert.assertFalse(user.isStatus());
    }
}