java - 保存后，如何将MongoDB集合加载到Java程序数据结构中？

我开始使用monogDB在Java程序中保存和加载文件，但是在将数据库重新加载到我的程序时遇到了麻烦。当我通过Mongo Compass检查时，我的保存方法完全可以工作并创建了Mongo数据库，我的主要问题是我希望它将那些数据库值加载回我的数组中，该数组在运行代码时存储所有信息。

现在，当我关闭并打开Java代码并输入load方法时，它不会检索已保存的条目

  private static void loadFile(String[] name) {
        try (MongoClient mongoClient = (MongoClient) MongoClients.create(System.getProperty("mongodb.uri"))) {
            MongoDatabase sampleTrainingDB = mongoClient.getDatabase("testDB");
            MongoCollection<Document> gradesCollection = sampleTrainingDB.getCollection("collection");

            // find one document with new Document
            Document document = gradesCollection.find(new Document("title", "Customer")).first();
        }
    }

这些是存储在我的字符串数组中的值

[Jacky, Becky, Becky, vacant, Jacky, amy, vacant, vacant, amy, vacant, Jackie, vacant, vacant, Jackie, Jackie, Annie, vacant, vacant, Annie, vacant, Maria, vacant, vacant, Maria, vacant, vacant, Maria, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant, vacant]

这是我的MongoDB的图片：View_Img



我只需要将它加载回我的数组中，这样我的程序就可以记住以前的条目。

*这是我保存文件的方式*

private static void saveFile(String[] name) {

        // Creating a Mongo client
        MongoClient mongo = new MongoClient("localhost", 27017);

        // Creating Credentials
        MongoCredential credential;
        credential = MongoCredential.createCredential("sampleUser", "trainDb",
                "password".toCharArray());
        System.out.println("Connected to the database successfully");

        //Accessing the database
        MongoDatabase database = mongo.getDatabase("testDB");

        //Creating a collection
        System.out.println("Collection created successfully");

        // Retrieving a collection
        MongoCollection<Document> collection = database.getCollection("collection");
        System.out.println("Collection myCollection selected successfully");

        for (int i = 0; i < 42; i++) {
            if (!name[i].equals("vacant") && (i == 0 || !name[i - 1].equals(name[i]))) {
                Document document = new Document("title", "Customer")
                        .append("Name", name[i])
                        .append("Seats", i + 1);
                collection.insertOne(document);
            }
        }
        System.out.println("Document inserted successfully");

    }

有谁可以帮助我吗 ？

最佳答案

我更新了您的loadFile方法以获取名称数组。

private static void loadFile(String[] name) {

    try (MongoClient mongoClient = MongoClients.create(System.getProperty("mongodb.uri"))) {

        MongoDatabase sampleTrainingDB = mongoClient.getDatabase("testDB");
        MongoCollection<Document> gradesCollection = sampleTrainingDB.getCollection("collection");

         // find one document with new Document
        Document document = gradesCollection.find(new Document("title", "Customer")).first();

        /** Code added from here to the end of the method      **/
        /** Find all documents and get the names into an array **/

        // First we will load the documents in to a List collection
        List<Document> list = new ArrayList<>();
        gradesCollection.find(new Document("title", "Customer"))
                        .into(list);
        // From the list of we extract the name field and store in a string array
        String [] names = list.stream()
                               .map(doc -> doc.get("name"))
                               .toArray(String[]::new);
        System.out.println(Arrays.toString(names));
    }
}

请注意，我还更改了MongoClient创建方法。