如何在 Spring Boot 中初始化一次 MongoClient 并使用它的方法？

Question

您好，我正在尝试在 Spring Boot 中成功连接后导出 MongoClient，并且我正在尝试在其他文件中使用它，这样我就不必每次需要更改时都调用连接我的 MongoDB 数据库。

连接非常简单，但目标是将应用程序连接到我的数据库一次，然后通过将其导入任何 Java 文件中的任何位置使用它。

谢谢

Answer 1

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。

(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();
    }
}

CommandLineRunner 的 run 方法的用法（所有示例都以类似方式运行）：

@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)。此配置用于使用 Spring Data MongoDB API 处理 MongoDB 数据库：MongoOperations（及其实现MongoTemplate）和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（在主题 2 中），但另外使用 @EnableMongoRepositories 进行注释。在这种情况下，我们将使用MongoRepository 接口方法将集合数据作为Java 对象获取。

存储库：

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

}

代表test3 集合文档的Test3.java POJO 类：

public class Test3 {

    private String id;
    private String fld;

    public Test3() {    
    }

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

以下方法获取文档并作为 Java 对象打印：

@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);
}

Answer 2

    **Pom Changes :**
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-mongodb</artifactId>
            </dependency>
    
            <!-- jpa, crud repository -->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
    **Main Application :**
    
    @SpringBootApplication(exclude = {
            MongoAutoConfiguration.class,
            MongoDataAutoConfiguration.class
    })
    public class Application {
    public static void main(String[] args) {
            SpringApplication.run(Application.class, args);
        }
    }
    
**MongoConfig Class :**

@Configuration
@EnableMongoRepositories({"com.repository.mongo"})
public class MongoConfig {

    private final MongoProperties properties;

    public MongoConfig(MongoProperties properties) {
        this.properties = properties;
    }

    @Bean
    public MongoClient mongo() throws IOException {
        log.info("Creating mongo client. Socket timeout: {}, request timeout: {}",
                properties.getSocketTimeout(), properties.getConnectTimeout()
        );
        MongoCredential credential = MongoCredential.createCredential(properties.getUsername(), properties.getDatabase(), readPassword(properties.getPasswordFilePath()).toCharArray());

        MongoClientSettings settings = MongoClientSettings.builder()
                .credential(credential)
                .applyToSocketSettings(builder -> builder.readTimeout(properties.getSocketTimeout().intValue(), TimeUnit.MILLISECONDS).connectTimeout(properties.getConnectTimeout().intValue(), TimeUnit.MILLISECONDS))
                .applyToClusterSettings(builder ->
                        builder.hosts(Arrays.asList(new ServerAddress(properties.getHost(), properties.getPort()))).requiredReplicaSetName(properties.getReplicaSet()))
                .build();

        return MongoClients.create(settings);
    }


    @Bean
    public MongoDatabase database() throws IOException {
        // Allow POJOs to be (de)serialized
        CodecRegistry extendedRegistry = fromRegistries(
                MongoClientSettings.getDefaultCodecRegistry(),
                fromProviders(PojoCodecProvider.builder().automatic(true).build())
        );
        return mongo().getDatabase(properties.getDatabase()).withCodecRegistry(extendedRegistry);
    }

    @Bean
    public MongoTemplate mongoTemplate() throws IOException {
        return new MongoTemplate(mongo(), properties.getDatabase());
    }

    @PreDestroy
    public void destroy() throws IOException {
        mongo().close();
    }

    private String readPassword(String path) throws IOException {
       // return Files.readString(Paths.get(path));
        return "****";
    }

}