Mongodb/Java db.collection.foo() not useable

Question

Summary - It seems as if all examples to use Mongodb commands within java start with db.collection.someMongoMethod(). For example db.collection.update() or db.collection.updateMany(). I have not found any description on the web as to what db.collection represents or how to create this object(s). It is just assumed that I should know.

Problem - How do I get db.collection.foo() to resolve in Java? I would like to run the db.collection.updateMany() or any other mongodb method within a java method. Below are my sample method attempts with resulting compile errors shown. And the one method I got compile which failed at runtime. The runtime error will follow after the code block.

Methods Attempted -

public void renameField(MongoDatabase db, MongoCollection<org.bson.Document> bsonCollection, String oldField, String newField) {
        
        // Students cannot be resolved or is not a field
        //db.students.update({oldField: {$exists: true}}, {$rename:{oldField:newField}}, false, true);

        // bsonCollection cannot be resolved or is not a field
        //db.bsonCollection.update({oldField: {$exists: true}}, {$rename:{oldField:newField}}, false, true);

        // Wants to add cast to bsonCollection
        //bsonCollection.update({oldField: {$exists: true}}, {$rename:{oldField:newField}}, false, true);

        // Wants to change method to receiver cast
        //((Object) bsonCollection).update({oldField: {$exists: true}}, {$rename:{oldField:newField}}, false, true);

        // Wants to change arguments to one of 8 possible cases
        //bsonCollection.updateMany({oldField: {$exists: true}}, {$rename:{oldField:newField}}, false, true);

        Document filter = new Document(oldField, "{$exists: true}");
        Document update = new Document("$rename", "{"+oldField+":"+newField+"}");
        //Remove arguments to match (bson,bson) or change to updateOne
        //bsonCollection.updateMany(filter.toBsonDocument(), update.toBsonDocument(), false, true);

        bsonCollection.updateMany(filter.toBsonDocument(), update.toBsonDocument());

    }

Runtime Error - The runtime error using collection.updateMany.

2021-06-12 11:49:06 ERROR o.a.c.c.C.[.[.[.[dispatcherServlet].log(175) - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is ongodb.MongoWriteException: Modifiers operate on fields but we found type string instead. For example: {$mod: {<field>: ...}} not {$rename: "{name:firstName}"}] with root cause
com.mongodb.MongoWriteException: Modifiers operate on fields but we found type string instead. For example: {$mod: {<field>: ...}} not {$rename: "{name:firstName}"}
    at com.mongodb.client.internal.MongoCollectionImpl.executeSingleWriteRequest(MongoCollectionImpl.java:1017)
    at com.mongodb.client.internal.MongoCollectionImpl.executeUpdate(MongoCollectionImpl.java:993)
    at com.mongodb.client.internal.MongoCollectionImpl.updateMany(MongoCollectionImpl.java:624)
    at com.mongodb.client.internal.MongoCollectionImpl.updateMany(MongoCollectionImpl.java:619)
    at com.myapp.service.CollectionServiceImpl.renameField(CollectionServiceImpl.java:238)
    at com.myapp.service.CollectionServiceImpl.processCollection(CollectionServiceImpl.java:94)
    at com.myapp.service.DatabaseServiceImpl.updateDatabase(DatabaseServiceImpl.java:256)
    at com.myapp.service.DatabaseServiceImpl.processDatabase(DatabaseServiceImpl.java:122)
    at com.myapp.service.DatabaseServiceImpl.processMongoChanges(DatabaseServiceImpl.java:72)
    at com.myapp.controller.DatabaseController.modifyMongo(DatabaseController.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Build Environment - I am using spring boot 2.4.5, eclipse, Java 8, and Mongodb 4.4. below is the relevant pom file.

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>${commons-lang3.version}</version><!--$NO-MVN-MAN-VER$-->
        </dependency>
    </dependencies>

Frustration - In all the online examples and documentation for executing mongodb commands using java, they all start with db.collection.someMethod(). However, I have yet to find a complete example that shows me that objects make up db.collection.

geobreze · Accepted Answer · 2021-06-12 18:54:35Z

1

Basically, db.collectionName is simplified syntax for db.getCollection("collectionName").

Everything that described as a BSON document in Mongo API reference should be a BSON document (for example, org.bson.Document) in your Java code. In your concrete example with $rename, the documentation says

The $rename operator updates the name of a field and has the following form:

{$rename: { <field1>: <newName1>, <field2>: <newName2>, ... } }

So, the value of $rename is a BSON document. Java implementation should be

Document renameOperator = new Document("$rename", new Document(oldField, newField))

But in your implementation value for $rename is a string, not BSON.

answered Jun 12, 2021 at 18:54

geobreze

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1 Comment

Bill Snee Over a year ago

Thanks for the clarification. I figured it was something simple I was missing. Also, I appreciate the example of how to use the BSON Document.

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