By kswaughs | Monday, June 1, 2020

Spring JdbcTemplate ResultSetExtractor Junit test example

This example shows how to write junit to test spring ResultSetExtractor functionality while mocking JdbcTemplate with Mockito.

This also increases code coverage of ResultSetExtractor code.

Below is the DAO class that returns Map of employees with ResultSetExtractor using Lambdas

Spring JdbcTemplate ResultSetExtractor Example with Lambdas
package com.kswaughs.dao;

import java.sql.ResultSet;
import java.util.HashMap;
import java.util.Map;

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

import com.kswaughs.beans.Employee;

@Repository
public class EmployeeDAO {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    public Map<Integer, Employee> getEmployeeMap() {

        return jdbcTemplate.query("SELECT ID, NAME, STATUS FROM EMPLOYEE",

            (ResultSet rs) -> {

                Map<Integer, Employee> employeeMap = new HashMap<>();

                while (rs.next()) {

                    Employee employee = new Employee();

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

                    employeeMap.put(employee.getId(), employee);
                }

                return employeeMap;
        });
    }
}

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

Spring JdbcTemplate ResultSetExtractor Junit test example
package com.kswaughs.dao;

import static org.mockito.Mockito.when;

import java.sql.ResultSet;
import java.util.Map;

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.ResultSetExtractor;

import com.kswaughs.beans.Employee;

@RunWith(MockitoJUnitRunner.class)
public class EmployeeDAOTest {

    @Mock
    private JdbcTemplate jdbcTemplate;

    @InjectMocks
    private EmployeeDAO employeeDAO;

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

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

                ResultSetExtractor<Map<Integer, Employee>> resultSetExtractor = 
                    (ResultSetExtractor<Map<Integer, Employee>>) invocation.getArgument(1);
                
                ResultSet rs = Mockito.mock(ResultSet.class);
                
                // two times it returns true and third time returns false.
                when(rs.next()).thenReturn(true, true, false);

                // 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);

                return resultSetExtractor.extractData(rs);
        });

        Map<Integer, Employee> employeeMap = employeeDAO.getEmployeeMap();
        
        // Assert First Row
        assertFirstUser(employeeMap.get(506));

        // Assert Second Row
        assertSecondUser(employeeMap.get(400));
    }

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

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