如何在Spring Boot中初始化MongoClient一次并使用其方法? [英] How to initialize MongoClient once in Spring Boot and use its methods?

问题描述

你好，我试图在Spring Boot中成功连接后导出 MongoClient ，并且试图在其他文件中使用它，这样我就不必每次都调用连接了需要在我的MongoDB数据库中进行更改.

Hello I am trying to export the MongoClient after a successful connection in Spring Boot and I am trying to use it in other files so that I do not have to call the connection every single time that I need to make changes in my MongoDB database.

连接非常简单，但是目标是将应用程序连接到我的数据库一次，然后将其导入任何Java文件中，然后在需要的地方使用它.

The connection is pretty simple but the goal would be to connect the application to my database once and then use it wherever I want by importing it in any Java file.

谢谢

推荐答案

以下是创建 MongoClient 实例，在Spring Boot应用程序中配置和使用它的几种方法.

Here are couple of ways of creating an instance of MongoClient, configuring and using it within the Spring Boot application.

(1)使用基于Java的元数据注册Mongo实例:

@Configuration
public class AppConfig {
    public @Bean MongoClient mongoClient() {
        return MongoClients.create();
    }
}

使用 CommandLineRunner 的 run 方法(所有示例均以类似方式运行):

@Autowired 
MongoClient mongoClient;

// Retrieves a document from the "test1" collection and "test" database.
// Note the MongoDB Java Driver API methods are used here.
private void getDocument() {
    MongoDatabase database = client.getDatabase("test");
    MongoCollection<Document> collection = database.getCollection("test1");
    Document myDoc = collection.find().first();
    System.out.println(myDoc.toJson());
}

(2)使用AbstractMongoClientConfiguration类进行配置并与MongoOperations一起使用:

@Configuration
public class MongoClientConfiguration extends AbstractMongoClientConfiguration {

    @Override
    public MongoClient mongoClient() {
        return MongoClients.create();
    }

    @Override
    protected String getDatabaseName() {
        return "newDB";
    }
}

请注意，您可以设置可以连接的数据库名称( newDB ).此配置用于通过Spring Data MongoDB API与MongoDB数据库一起使用: MongoOperations (及其实现 MongoTemplate )和 MongoRepository .

Note you can set the database name (newDB) you can connect to. This configuration is used to work with MongoDB database using Spring Data MongoDB APIs: MongoOperations (and its implementation MongoTemplate) and the MongoRepository.

@Autowired 
MongoOperations mongoOps;

// Connects to "newDB" database, and gets a count of all documents in the "test2" collection.
// Uses the MongoOperations interface methods.
private void getCollectionSize() {
    Query query = new Query();
    long n = mongoOps.count(query, "test2");
    System.out.println("Collection size: " + n);
}

(3)使用AbstractMongoClientConfiguration类进行配置并与MongoRepository一起使用

使用相同的配置 MongoClientConfiguration 类(主题2中的上的)，但还要使用 @EnableMongoRepositories 进行注释.在这种情况下，我们将使用 MongoRepository 接口方法将收集数据作为Java对象获取.

Using the same configuration MongoClientConfiguration class (above in topic 2), but additionally annotate with @EnableMongoRepositories. In this case we will use MongoRepository interface methods to get collection data as Java objects.

存储库:

@Repository
public interface MyRepository extends MongoRepository<Test3, String> {

}

代表 test3 集合文档的 Test3.java POJO类:

The Test3.java POJO class representing the test3 collection's document:

public class Test3 {

    private String id;
    private String fld;

    public Test3() {    
    }

    // Getter and setter methods for the two fields
    // Override 'toString' method
    ...
}

以下获取文档并作为Java对象打印的方法:

The following method to get documents and print as Java objects:

@Autowired 
MyRepository repository;

// Method to get all the `test3` collection documents as Java objects.
private void getCollectionObjects() {
    List<Test3> list = repository.findAll();
    list.forEach(System.out::println);
}

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