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Mock DriverManager.getconnection method for junit/mockito unit tests

Greenhorn

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posted 2 months ago

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I am a student and learning java, junit, mockito. How can i mock the DriverManager.getconnection method. I am new to junit and mockito and learning the use of the same. Any suggestion would be highly appreciated. Thanks in advance.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.my.config.project.dsexecutor.model.DSConfig;

public class dsexecutor {
    public JsonArray readTableDataAsJson(String sqlQuery, DSConfig dataConfig) throws SQLException {

String host = dataConfig.getHost();
        String httpPath = dataConfig.getHttpPath();
        String accessToken = dataConfig.getAccessToken();
        String username = dataConfig.getUsername();
   
        String jdbcString = String.format(
                "jdbc:datatest://%s:443;EnableArrow=0;transportMode=http;ssl=1;httpPath=%s;AuthMech=3;UID=token;PWD=%s",
                host, httpPath, accessToken);

try (Connection conn = DriverManager.getConnection(jdbcString, username, accessToken);
                Statement stmt = conn.createStatement()) {
            try (ResultSet resultSet = stmt.executeQuery(sqlQuery)) {
                JsonArray jsonArray = new JsonArray();
                while (resultSet.next()) {
                    JsonObject jsonObject = new JsonObject();
                    ResultSetMetaData metaData = resultSet.getMetaData();
                    int numColumns = metaData.getColumnCount();
                    for (int i = 1; i <= numColumns; i++) {
                        String columnName = metaData.getColumnName(i);
                        String columnValue = resultSet.getString(i);
                        jsonObject.addProperty(columnName, columnValue);
                    }
                    jsonArray.add(jsonObject);
                }
                return jsonArray;
            }
        }
    }
}

Stephan van Hulst

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posted 2 months ago

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Welcome to CodeRanch!

Mockito can't mock static methods. At least, not in the last version I worked with.

You could use a different tool such as PowerMock to mock static methods, but you really shouldn't have to: If you're looking up a service using a static method such as DriverManager.getConnection(), then you haven't designed your class well. Services should be injected as a constructor or method parameter.

In this particular case, you must refactor your code so that your class has an instance field of type DataSource that you initialize in the constructor. Instead of calling DriverManager.getConnection(), you call dataSource.getConnection().

In your unit test, you can mock the DataSource that is passed to the constructor of your class.

Tim Holloway

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posted 2 months ago

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Welcome to the Ranch, Arron!

Actually, I believe that Mockito has been able to mock statics for several years now (before that, extra help was needed).

But I wouldn't be using mocks there in any event.

There is a JUnit test capability that specifically tests database logic and it doesn't need mocks to do that. That's my preferred method.

In fact, mocks are my test of last resort. Mockito mocks in particular can be more trouble than they are worth, especially when you're attempting to get data from a mocked object.

However, this link seems to be addressing your problem using mocks: https://dzone.com/articles/mockito-basic-example-using-jdbc

The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.

You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.