Convert all the mysql table data into JSON in spring boot - mysql

Question

I want to just specify the table name and it will automatically convert all of its data to JSON Format
I have tried a code that is storing the data from table into JSON using JDBC .
public class DataBaseToJson {
public static ResultSet RetrieveData() throws Exception {
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
String mysqlUrl = "jdbc:mysql://localhost/studentsDB?autoReconnect=true&useSSL=false";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "root");
Statement statement = con.createStatement();
ResultSet resultSet = statement.executeQuery("Select * from students");
return resultSet;
}
public static void main(String args[]) throws Exception {
JSONObject jsonObject = new JSONObject();
JSONArray array = new JSONArray();
ResultSet resultSet = RetrieveData();
while (resultSet.next()) {
JSONObject record = new JSONObject();
record.put("students ID", resultSet.getInt("students_id"));
record.put("students Name", resultSet.getString("students_name"));
array.add(record);
}
jsonObject.put("students Information", array);
try {
FileWriter file = new FileWriter("output.json");
file.write(jsonObject.toJSONString());
file.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
I don't want to specify the fileds in a file. I want to make it generic so that we could only put the table name and it will automatically convert all the data from that table and save into a JSON file.

Answer 1

public static void main(String args[]) throws Exception {
String tableName = "books";
Connection connection = createConnection();
JSONArray array = new JSONArray();
JSONObject jsonObject = new JSONObject();
List<String> columns = loadColumns(connection, tableName);
ResultSet dataSet = loadData(connection, tableName);
while (dataSet.next()) {
JSONObject record = new JSONObject();
for (String column : columns) {
record.put(column, dataSet.getObject(column));
}
array.add(record);
}
jsonObject.put(tableName, array);
try {
FileWriter file = new FileWriter("output.json");
file.write(jsonObject.toJSONString());
file.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private static Connection createConnection() throws SQLException {
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
String mysqlUrl = "jdbc:mysql://localhost/library?autoReconnect=true&useSSL=false";
Connection connection = DriverManager.getConnection(mysqlUrl, "root", "root");
return connection;
}
public static List<String> loadColumns(Connection connection, String tableName) throws SQLException {
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("SELECT COLUMN_NAME FROM `INFORMATION_SCHEMA`.`COLUMNS` WHERE TABLE_NAME LIKE '"+tableName+"'");
List<String> columnsName = new ArrayList<String>();
while(resultSet.next()) {
columnsName.add(resultSet.getString("COLUMN_NAME"));
}
return columnsName;
}
public static ResultSet loadData(Connection connection, String tableName) throws SQLException {
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery("Select * from "+tableName+"");
return resultSet;
}

Answer 2

You can select list of columns for given table using INFORMATION_SCHEMA:
SELECT COLUMN_NAME FROM `INFORMATION_SCHEMA`.`COLUMNS` WHERE TABLE_NAME LIKE 'table_name'
Now, convert ResultSet from above query to List<String> of column names. After that we can use it to convert final ResultSet to JSON Object.
Pseudocode:
Connection connection = createConnection();
List<String> columns = loadColumns(connection, tableName);
ResultSet dataSet = loadData(connection, tableName);
while (dataSet.next()) {
JSONObject record = new JSONObject();
for (String column : columns) {
record.put(column, dataSet.getObject(column));
}
array.add(record);
}
// save array to file
When ResultSet is huge we should consider to use Streaming API from Jackson or Gson libraries to avoid "out of memory" problem.
See also:
How to get database structure in MySQL via query
Jackson Streaming API
Jackson - Processing model: Streaming API
Gson Streaming
Update
It looks like we do not event need to select column names using extra SQL query because ResultSet has getMetaData method:
Retrieves the number, types and properties of this ResultSet object's
columns.
See also:
ResultSetMetaData class