Java开发中如何进行持久化和数据存储优化

import java.sql.*;

public class MySQLPersistence {
    private static final String URL = "jdbc:mysql://localhost:3306/test";
    private static final String USER = "root";
    private static final String PASSWORD = "password";

    public void saveData(String data) {
        try {
            Connection connection = DriverManager.getConnection(URL, USER, PASSWORD);
            Statement statement = connection.createStatement();
            String query = "INSERT INTO data_table (data) VALUES ('" + data + "')";
            statement.executeUpdate(query);
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public String loadData() {
        String data = null;
        try {
            Connection connection = DriverManager.getConnection(URL, USER, PASSWORD);
            Statement statement = connection.createStatement();
            String query = "SELECT data FROM data_table";
            ResultSet resultSet = statement.executeQuery(query);
            if (resultSet.next()) {
                data = resultSet.getString("data");
            }
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return data;
    }
}

import com.mongodb.*;

public class MongoDBPersistence {
    private MongoClient mongoClient;
    private DB database;
    private DBCollection collection;

    public MongoDBPersistence() {
        this.mongoClient = new MongoClient("localhost", 27017);
        this.database = mongoClient.getDB("test");
        this.collection = database.getCollection("data_collection");
    }

    public void saveData(String data) {
        BasicDBObject document = new BasicDBObject();
        document.put("data", data);
        collection.insert(document);
    }

    public String loadData() {
        BasicDBObject query = new BasicDBObject();
        DBCursor cursor = collection.find(query);
        String data = null;
        while (cursor.hasNext()) {
            DBObject document = cursor.next();
            data = document.get("data").toString();
        }
        cursor.close();
        return data;
    }
}