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BAEL-4789 Check if a database table exists (#10565) 

* BAEL-4789 Check if a database table exists

* BAEL-4789 fix db credentials

* BAEL-4789 fix test method name
This commit is contained in:
mdabrowski-eu 2021-03-21 18:38:10 +01:00 committed by GitHub
parent 45764829f7
commit dd288575da
3 changed files with 126 additions and 0 deletions
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21
persistence-modules/core-java-persistence-2/src/main/java/com/baeldung/tableexists/DatabaseConfig.java Normal file
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package com.baeldung.tableexists;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
class DatabaseConfig {
static Connection connect() throws ClassNotFoundException, SQLException {
Class.forName("org.h2.Driver");
String url = "jdbc:h2:mem:testdb";
return DriverManager.getConnection(url, "user", "password");
}
static void createTables(Connection connection) throws SQLException {
connection.createStatement().executeUpdate("create table EMPLOYEE (id int primary key auto_increment, name VARCHAR(255))");
}
static void dropTables(Connection connection) throws SQLException {
connection.createStatement().executeUpdate("drop table EMPLOYEE");
}
}

35
persistence-modules/core-java-persistence-2/src/main/java/com/baeldung/tableexists/TableChecker.java Normal file
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package com.baeldung.tableexists;
import java.sql.*;
class TableChecker {
static void printAllTables(Connection connection, String tableName) throws SQLException {
DatabaseMetaData databaseMetaData = connection.getMetaData();
ResultSet resultSet = databaseMetaData.getTables(null, null, tableName, new String[] {"TABLE"});
while (resultSet.next()) {
String name = resultSet.getString("TABLE_NAME");
String schema = resultSet.getString("TABLE_SCHEM");
System.out.println(name + " on schema " + schema);
}
}
static boolean tableExists(Connection connection, String tableName) throws SQLException {
DatabaseMetaData meta = connection.getMetaData();
ResultSet resultSet = meta.getTables(null, null, tableName, new String[] {"TABLE"});
return resultSet.next();
}
static boolean tableExistsSQL(Connection connection, String tableName) throws SQLException {
PreparedStatement preparedStatement = connection.prepareStatement("SELECT count(*) " +
"FROM information_schema.tables " +
"WHERE table_name = ?" +
"LIMIT 1;");
preparedStatement.setString(1, tableName);
ResultSet resultSet = preparedStatement.executeQuery();
resultSet.next();
return resultSet.getInt(1) != 0;
}
}

70
persistence-modules/core-java-persistence-2/src/test/java/com/baeldung/tableexists/TableCheckerTest.java Normal file
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package com.baeldung.tableexists;
import org.junit.jupiter.api.Test;
import java.sql.Connection;
import java.sql.SQLException;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
class TableCheckerUnitTest {
@Test
void givenCreatedTable_shouldFindTable() throws SQLException, ClassNotFoundException {
// given
Connection connection = DatabaseConfig.connect();
DatabaseConfig.createTables(connection);
// when
boolean tableExists = TableChecker.tableExists(connection, "EMPLOYEE");
// then
TableChecker.printAllTables(connection, null);
assertTrue(tableExists);
DatabaseConfig.dropTables(connection);
}
@Test
void givenCreatedTable_shouldFindTableWithSQL() throws SQLException, ClassNotFoundException {
// given
Connection connection = DatabaseConfig.connect();
DatabaseConfig.createTables(connection);
// when
boolean tableExists = TableChecker.tableExistsSQL(connection, "EMPLOYEE");
// then
TableChecker.printAllTables(connection, null);
assertTrue(tableExists);
DatabaseConfig.dropTables(connection);
}
@Test
void givenNoTable_shouldNotFindTable() throws SQLException, ClassNotFoundException {
// given
Connection connection = DatabaseConfig.connect();
// when
boolean tableExists = TableChecker.tableExists(connection, "EMPLOYEE");
// then
TableChecker.printAllTables(connection, null);
assertFalse(tableExists);
}
@Test
void givenNoTable_shouldNotFindTableWithSQL() throws SQLException, ClassNotFoundException {
// given
Connection connection = DatabaseConfig.connect();
// when
boolean tableExists = TableChecker.tableExistsSQL(connection, "EMPLOYEE");
// then
TableChecker.printAllTables(connection, null);
assertFalse(tableExists);
}
}