使用spring-data-mongodb存储库持久化路径对象

Question

在一个项目中，我使用spring-boot-starter-data-mongodb:2.5.3，因此spring-data-mongodb:3.2.3，并有一个实体类，简化如下:

@Document
public class Task {
@Id
private final String id;
private final Path taskDir;
...
// constructor, getters, setters
}

使用默认的Spring MongoDB存储库，允许通过其id检索任务。

Mongo配置如下:

@Configuration
@EnableMongoRepositories(basePackages = {
"path.to.repository"
}, mongoTemplateRef = MongoConfig.MONGO_TEMPLATE_REF)
@EnableConfigurationProperties(MongoSettings.class)
public class MongoConfig extends MongoConfigurationSupport {
private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
public static final String MONGO_TEMPLATE_REF = "mongoAlTemplate";
private final MongoSettings mongoSettings;
@Autowired
public MongoConfig(final MongoSettings mongoSettings) {
this.mongoSettings = mongoSettings;
}
@Bean(name = "ourMongo", destroyMethod = "close")
public MongoClient ourMongoClient() {
MongoCredential credential =
MongoCredential.createCredential(mongoSettings.getUser(),
mongoSettings.getDb(),
mongoSettings.getPassword());
MongoClientSettings clientSettings = MongoClientSettings.builder()
.readPreference(ReadPreference.primary())
// enable optimistic locking for @Version and eTag usage
.writeConcern(WriteConcern.ACKNOWLEDGED)
.credential(credential)
.applyToSocketSettings(
builder -> builder.connectTimeout(15, TimeUnit.SECONDS)
.readTimeout(1, TimeUnit.MINUTES))
.applyToConnectionPoolSettings(
builder -> builder.maxConnectionIdleTime(10, TimeUnit.MINUTES)
.minSize(5).maxSize(20))
//        .applyToClusterSettings(
//            builder -> builder.requiredClusterType(ClusterType.REPLICA_SET)
//                .hosts(Arrays.asList(new ServerAddress("host1", 27017),
//                                     new ServerAddress("host2", 27017)))
//                .build())
.build();
return MongoClients.create(clientSettings);
}
@Override
@Nonnull
protected String getDatabaseName() {
return mongoSettings.getDb();
}
@Bean(name = MONGO_TEMPLATE_REF)
public MongoTemplate ourMongoTemplate() throws Exception {
return new MongoTemplate(ourMongoClient(), getDatabaseName());
}
}

在试图通过taskRepository.save(task)保存任务Java最终在StackOverflowError

java.lang.StackOverflowError
at java.lang.ThreadLocal.get(ThreadLocal.java:160)
at java.util.concurrent.locks.ReentrantReadWriteLock$Sync.tryReleaseShared(ReentrantReadWriteLock.java:423)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(AbstractQueuedSynchronizer.java:1341)
at java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.unlock(ReentrantReadWriteLock.java:881)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:239)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:201)
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:87)
at org.springframework.data.mapping.context.MappingContext.getRequiredPersistentEntity(MappingContext.java:73)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writePropertyInternal(MappingMongoConverter.java:740)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeProperties(MappingMongoConverter.java:657)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:633)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writePropertyInternal(MappingMongoConverter.java:746)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeProperties(MappingMongoConverter.java:657)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.writeInternal(MappingMongoConverter.java:633)
...

在Task类中注释路径对象taskDir与@Transient我能够坚持任务，所以问题似乎与Java/Spring/MongoDB无法直接处理Path对象有关。

我的下一个尝试是在MongoConfig类中配置一个自定义转换器，以在Path和String表示之间进行转换:

@Override
protected void configureConverters(
MongoCustomConversions.MongoConverterConfigurationAdapter converterConfigurationAdapter) {
LOG.info("configuring converters");
converterConfigurationAdapter.registerConverter(new Converter<Path, String>() {
@Override
public String convert(@Nonnull Path path) {
return path.normalize().toAbsolutePath().toString();
}
});
converterConfigurationAdapter.registerConverter(new Converter<String, Path>() {
@Override
public Path convert(@Nonnull String path) {
return Paths.get(path);
}
});
}

，但错误仍然存在。然后，我定义了Task对象和DBObject对象之间的直接转换，如本指南

所示。

@Override
protected void configureConverters(
MongoCustomConversions.MongoConverterConfigurationAdapter converterConfigurationAdapter) {
LOG.info("configuring converters");
converterConfigurationAdapter.registerConverter(new Converter<Task, DBObject>() {
@Override
public DBObject convert(@Nonnull Task source) {
DBObject dbObject = new BasicDBObject();
if (source.getTaskDirectory() != null) {
dbObject.put("taskDir", source.getTaskDirectory().normalize().toAbsolutePath().toString());
}
...
return dbObject;
}
});
}

，我仍然得到一个StackOverflowError作为回报。通过我添加的日志语句，我看到Spring调用了configureConverters方法，因此应该注册了自定义转换器。

为什么我仍然得到StackOverflowError虽然?我需要如何告诉Spring将Path对象视为Strings，同时持久化并在读取时将String值转换为Path对象?

更新:

---

我现在已经按照官方文档中给出的示例，并将转换器重构为它自己的类

import org.bson.Document;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.convert.WritingConverter;
import javax.annotation.Nonnull;
@WritingConverter
public class TaskWriteConverter implements Converter<Task, Document> {
@Override
public Document convert(@Nonnull Task source) {
Document document = new Document();
document.put("_id", source.getId());
if (source.getTaskDir() != null) {
document.put("taskDir", source.getTaskDir().normalize().toAbsolutePath().toString());
}
return document;
}
}

MongoConfig类中的配置现在看起来像这样:

@Override
protected void configureConverters(
MongoCustomConversions.MongoConverterConfigurationAdapter adapter) {
LOG.info("configuring converters");
adapter.registerConverter(new TaskWriteConverter());
adapter.registerConverter(new TaskReadConverter());
adapter.registerConverter(new Converter<Path, String>() {
@Override
public String convert(@Nonnull Path path) {
return path.normalize().toAbsolutePath().toString();
}
});
adapter.registerConverter(new Converter<String, Path>() {
@Override
public Path convert(@Nonnull String path) {
return Paths.get(path);
}
});
}

将org.springframework.data的日志级别更改为debug后，我在日志中看到这些转换器也被拾取:

2021-09-23 14:09:20.469 [INFO ] [           main] MongoConfig                              configuring converters 
2021-09-23 14:09:20.480 [DEBUG] [           main] CustomConversions                        Adding user defined converter from class com.acme.Task to class org.bson.Document as writing converter. 
2021-09-23 14:09:20.480 [DEBUG] [           main] CustomConversions                        Adding user defined converter from class org.bson.Document to class com.acme.Task as reading converter. 
2021-09-23 14:09:20.481 [DEBUG] [           main] CustomConversions                        Adding user defined converter from interface java.nio.file.Path to class java.lang.String as writing converter. 
2021-09-23 14:09:20.481 [DEBUG] [           main] CustomConversions                        Adding user defined converter from class java.lang.String to interface java.nio.file.Path as reading converter.

然而，我看到大多数转换器被添加了多次，也就是说，在应用程序到达存储库上的save方法之前，我发现Adding converter from class java.lang.Character to class java.lang.String as writing converter.的日志实际上是4次。由于我的自定义转换器只在第三次添加所有这些转换器出现在日志中，我有一种感觉，它们在最后一次"迭代"中不知怎的被覆盖为日志。不要包括我的自定义转换器。

重现该问题的测试用例如下:

@ŚpringBootTest
@AutoConfigureMockMvc
@PropertySource("classpath:application-test.properties")
public class SomeIT {

@Autowired
private TaskRepository taskRepository;
...

@Test
public void testTaskPersistence() throws Exception {
Task task = new Task("1234", Paths.get("/home/roman"));
taskRepository.save(task);
}
...
}

test方法仅用于调查当前的持久性问题，在正常情况下根本不应该存在，因为集成测试测试大文件的上传及其预处理等。然而，由于Spring不能(至少看起来是这样)存储包含Path对象的实体，因此该集成测试失败。

请注意，对于简单的实体，我在使用概述的设置持久化它们时没有问题，并且我也在dockerized MongoDB中看到它们。

我还没有时间深入研究为什么Spring对Path对象有这样的问题，或者为什么我的自定义转换器在CustomConversions日志输出的最后一次迭代中突然消失了。

Answer 1

事实证明，mongoTemplate的配置方式是"覆盖"的。任何指定的自定义转换器，因此Spring不能使用这些转换器并将Path转换为String，反之亦然。

将MongoConfig更改为如下所示后，我终于能够使用自定义转换器，从而按预期持久化实体:

@Configuration
@EnableMongoRepositories(basePackages = {
"path.to.repository"
}, mongoTemplateRef = MongoConfig.MONGO_TEMPLATE_REF)
@EnableConfigurationProperties(MongoSettings.class)
public class MongoConfig extends MongoConfigurationSupport {
private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
public static final String MONGO_TEMPLATE_REF = "mongoAlTemplate";
private final MongoSettings mongoSettings;
@Autowired
public MongoConfig(final MongoSettings mongoSettings) {
this.mongoSettings = mongoSettings;
}
@Bean(name = "ourMongo", destroyMethod = "close")
public MongoClient ourMongoClient() {
MongoCredential credential =
MongoCredential.createCredential(mongoSettings.getUser(),
mongoSettings.getDb(),
mongoSettings.getPassword());
MongoClientSettings clientSettings = MongoClientSettings.builder()
.readPreference(ReadPreference.primary())
// enable optimistic locking for @Version and eTag usage
.writeConcern(WriteConcern.ACKNOWLEDGED)
.credential(credential)
.applyToSocketSettings(
builder -> builder.connectTimeout(15, TimeUnit.SECONDS)
.readTimeout(1, TimeUnit.MINUTES))
.applyToConnectionPoolSettings(
builder -> builder.maxConnectionIdleTime(10, TimeUnit.MINUTES)
.minSize(5).maxSize(20))
//        .applyToClusterSettings(
//            builder -> builder.requiredClusterType(ClusterType.REPLICA_SET)
//                .hosts(Arrays.asList(new ServerAddress("host1", 27017),
//                                     new ServerAddress("host2", 27017)))
//                .build())
.build();
LOG.info("Mongo client initialized. Connecting with user {} to DB {}",
mongoSettings.getUser(), mongoSettings.getDb());
return MongoClients.create(clientSettings);
}
@Override
@Nonnull
protected String getDatabaseName() {
return mongoSettings.getDb();
}
@Bean
public MongoDatabaseFactory ourMongoDBFactory() {
return new SimpleMongoClientDatabaseFactory(ourMongoClient(), getDatabaseName());
}
@Bean(name = MONGO_TEMPLATE_REF)
public MongoTemplate ourMongoTemplate() throws Exception {
return new MongoTemplate(ourMongoDBFactory(), mappingMongoConverter());
}
@Bean
public MappingMongoConverter mappingMongoConverter() throws Exception {
DbRefResolver dbRefResolver = new DefaultDbRefResolver(ourMongoDBFactory());
MongoCustomConversions customConversions = customConversions();
MongoMappingContext context = mongoMappingContext(customConversions);
MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, context);
// this one is actually needed otherwise the StackOverflowError re-appears!
converter.setCustomConversions(customConversions);
return converter;
}
@Bean
@Override
@Nonnull
public MongoCustomConversions customConversions() {
return  new MongoCustomConversions(
Arrays.asList(new PathWriteConverter(), new PathReadConverter())
);
}
}

因此，不是直接将MongoClient和数据库名称传递给mongoTemplate，而是将包含上述值的MongoDatabaseFactory对象和MappingMongoConverter对象作为输入传递给模板。

不幸的是，必须在mappingMongoConverter()方法中传递customConversion对象两次。如果不这样做，StackOverflowError将重新出现。

在给定的配置下，现在可以从Path转换到String，从String转换到Path，因此目前不需要从Task转换到Document，反之亦然。