DOCSP-47273: FAQ reorg (#644)

* DOCSP-47273: FAQ reorg

* edits

* pojo

* RM feedback

Author: norareidy

source/connection/connect.txt

@@ -4,6 +4,12 @@
 Connect to MongoDB
 ==================
 
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 2
+   :class: singlecol
+
 .. facet::
    :name: genre
    :values: reference
@@ -200,3 +206,118 @@ class. Select the tab that corresponds to your preferred class.
                  .build();
          MongoClient mongoClient = MongoClients.create(settings);
 
+Frequently Asked Questions
+--------------------------
+
+This section answers questions that may arise when
+connecting to MongoDB.
+
+Why are there two types of ``MongoClient`` in the Java driver?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are two types of ``MongoClient`` because we wanted a cleaner API
+for new users that didn't have the confusion of including multiple CRUD
+Frequently AsAPIs. We wanted to ensure that the new CRUD API was available in a Java
+package structure that would work well with Java module support
+introduced in Java 9.
+
+Which type of ``MongoClient`` should I use?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+New applications generally use the ``com.mongodb.client.MongoClient`` interface,
+which supports the following features:
+
+- Configuration with ``MongoClientSettings`` and ``ConnectionString``.  You can create
+  instances of this interface by using factory methods defined in the ``com.mongodb.client.MongoClients``
+  class.
+- Access to the CRUD API by using ``MongoDatabase``, and from there, ``MongoCollection``.
+
+Use the ``com.mongodb.MongoClient`` class if you require support for the legacy API, which supports
+the following features:
+
+- Configuration by using ``MongoClientOptions`` and ``MongoClientURI``.
+- Access to the CRUD API by using ``DB``, and from there, ``DBCollection``.  You can access this API
+  by using the ``getDB()`` method.
+
+For applications that require a mix of the new and legacy APIs, ``com.mongodb.MongoClient`` also supports
+the following features:
+
+- Configuration by using ``MongoClientSettings`` and ``ConnectionString``, the only difference
+  being that you create instances via constructors instead of a factory class.
+- Access to the CRUD API using ``MongoDatabase``, and from there, ``MongoCollection``.  You can access this
+  API by using the ``getDatabase()`` method.
+
+How do I prevent the "java.lang.NoClassDefFoundError: com/mongodb/MongoClient" error?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You might encounter a ``java.lang.NoClassDefFoundError`` exception when your
+Java runtime environment cannot locate a class file at runtime. When you
+attempt to run application code that uses the {+driver-long+}, you must include
+the appropriate driver JAR files on the classpath.
+
+If you receive this error after adding the {+driver-short+} JAR files to
+your classpath, check the following items in your environment:
+
+- The JAR files exist in the locations specified by the classpath.
+- The classpath syntax is correct.
+- If you define the classpath in an environment variable, the Java runtime
+  environment uses that variable.
+- If you use a dependency manager, it does not report any unresolvable conflicts.
+
+.. tip::
+
+   This error contains the package and class name, which can help you identify
+   which driver JAR might be missing from your classpath. To locate the
+   driver JAR that the error refers to, check each of the entries in the
+   :ref:`API documentation <java-api-landing>`.
+
+How do I prevent the "com.mongodb.MongoSecurityException" error?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Your application might throw this exception if you specify invalid or
+incorrectly formatted credentials when connecting to a MongoDB deployment.
+
+If you receive this error when you attempt to connect to a MongoDB deployment,
+check the following items in your code:
+
+- The connection URI corresponds to the correct MongoDB deployment.
+  To learn more about setting your connection URI, see :ref:`connection-uri`.
+
+- The credentials for the authentication mechanism that you specified are
+  correct. To learn how to specify your credentials, see the
+  :ref:`authentication-mechanisms` and :ref:`enterprise-authentication-mechanisms`
+  guides.
+
+- The name of the authentication database that you specified is correct. To
+  learn how to set up the users and roles for your MongoDB deployment, see
+  `Manage Users and Roles <https://www.mongodb.com/docs/manual/tutorial/manage-users-and-roles/>`__
+  in the Server documentation.
+
+How do I prevent the "IllegalStateException: state should be: open" error?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You might encounter this exception if you call an operation on a ``MongoClient``
+instance that closed its connections to MongoDB. Once the ``close()`` method
+is called on the ``MongoClient``, any further operation calls on that instance
+throw this exception.
+
+To avoid this exception, do not call operations on ``MongoClient`` instance
+after any code that calls ``close()`` on it.
+
+.. tip::
+
+   The code that closes the ``MongoClient`` instance might be difficult to
+   locate in certain cases. To locate potential sources of this exception,
+   search for the following cases:
+
+   - Calls to ``close()`` on a ``MongoClient`` instance
+   - Operation calls on a ``MongoClient`` instance that are outside the scope
+     of the try-with-resources statement in which the ``MongoClient`` is
+     declared
+
+   If your application uses a framework to manage the ``MongoClient``
+   such as Spring Boot, check the documentation of the framework to locate the
+   best practices for managing the connection behavior.
+
+   To learn more about accessing MongoDB from Spring Boot, see
+   `Spring Boot and MongoDB <https://www.mongodb.com/compatibility/spring-boot>`__.

source/connection/mongoclientsettings.txt

@@ -591,4 +591,4 @@ to MongoDB:
    :end-before: end SslSettings
    :language: java
    :emphasize-lines: 3-4
-   :dedent:
+   :dedent:

source/data-formats/document-data-format-bson.txt

@@ -89,3 +89,52 @@ for that tool:
 If you are not using one of the preceding tools, you can include it in
 your project by downloading the JAR file directly from the
 `sonatype repository <https://repo1.maven.org/maven2/org/mongodb/bson/>`__.
+
+Frequently Asked Questions
+--------------------------
+
+This section answers questions that may arise when using the BSON data format.
+
+How do I prevent the "IllegalArgumentException: Invalid BSON field name" error?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Your application might throw this exception if you pass an incorrectly formatted
+document to an operation and you are using {+driver-short+} v4.7 or earlier.
+
+.. note::
+
+   In driver versions v4.8 and later, this error message was replaced by one
+   that includes more specific details on what was incorrectly formatted.
+
+For example, the driver throws this error when you call an update operation
+and incorrectly omit the update operator as shown in the following code
+example:
+
+.. code-block:: java
+   :emphasize-lines: 4
+   :copyable: false
+
+   // incorrectly formatted update document
+   collection.updateOne(
+       new Document().append("name", "fizz"),
+       new Document().append("name", "buzz")
+   );
+
+To avoid this error, use the builder class for the appropriate operation.
+The driver offers builder classes to create syntactically correct BSON for
+MongoDB operations. The preceding example can be correctly expressed using
+the builder classes, as shown in the following code example:
+
+.. code-block:: java
+   :emphasize-lines: 7
+   :copyable: false
+
+   // Builder class imports
+   import static com.mongodb.client.model.Filters.*;
+   import static com.mongodb.client.model.Updates.*;
+
+   // ...
+
+   collection.updateOne(eq("name", "fizz"), set("name", "buzz"));
+
+To learn more about the available builders classes, see the :ref:`<java-builders>` guide.

source/data-formats/document-data-format-pojo.txt

@@ -206,16 +206,44 @@ see the following API documentation:
 - `getDefaultCodecRegistry() <{+api+}/apidocs/mongodb-driver-core/com/mongodb/MongoClientSettings.html?is-external=true#getDefaultCodecRegistry()>`__
 - `fromProviders() <{+api+}/apidocs/bson/org/bson/codecs/configuration/CodecRegistries.html#fromProviders(org.bson.codecs.configuration.CodecProvider...)>`__
 
-Summary
--------
-
-This guide describes how to convert data between BSON and the POJO format
-by performing the following tasks:
-
-- Instantiate a ``PojoCodecProvider`` which contains codecs that define how to
-  encode and decode data between BSON and the POJO fields.
-- Specify the **automatic** conversion behavior for the ``PojoCodecProvider``
-  to apply the ``Codecs`` to any class and its properties.
-- Add the ``PojoCodecProvider`` to a ``CodecRegistry``, and specify the
-  registry on an instance of a ``MongoDatabase`` or ``MongoCollection``.
-- Perform CRUD operations that use the sample POJO class.
+Frequently Asked Questions
+--------------------------
+
+This section answers questions that may arise when storing
+POJOs in MongoDB.
+
+Do I have to specify an ID field value myself?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+No, the ``PojoCodecProvider`` automatically generates an ObjectId.
+
+Can the ID field be a compound key?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Yes. For an example of this, see `our implementation <https://github.com/niccottrell/mongo-java-tests/blob/master/src/test/PojoCompoundIdTest.java>`__
+in Github.
+
+Can I use polymorphism in a POJO accessor?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Yes, by using a discriminator. For more information, see the :ref:`Discriminators
+<pojo-discriminators>` section of the POJO Customization guide.
+
+Can I mix private, protected, and public setters and getters?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+No. The native POJO codec assumes that getters and setters have the same
+modifiers for each field.
+
+For example, the following methods throws an exception during encoding:
+
+.. code-block:: java
+
+   private String getField();
+   public String setField(String x);
+
+How do I fix: "org.bson.codecs.configuration.CodecConfigurationException: Can't find a codec for class X."?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This exception means you must register a codec for the class since
+none exist.

source/data-formats/pojo-customization.txt

@@ -759,4 +759,57 @@ a codec for ``enum`` types if you need one, such as the one in the default
 codec registry.
 
 See the documentation on the :ref:`default codec registry <codecs-default-codec-registry>`
-For more information about how to register the codecs it includes.
+for more information about how to register the codecs it includes.
+
+Frequently Asked Questions
+--------------------------
+
+This section answers questions that may arise when defining
+data conversion logic.
+
+Can I control serialization of ``LocalDate``?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Yes, the {+driver-short+} v3.7 adds native support for ``JSR-310 Instant``,
+``LocalDate`` and ``LocalDateTime``.
+
+Can I serialize a ``java.util.Date`` as a string in format **yyyy-mm-dd**?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Yes, you can build your own codec for this class and add it to the registry.
+
+Add the codec to the first in the list of providers, before the default codec
+registry and before the ``PojoCodecProvider``:
+
+.. literalinclude:: /includes/faq/code-snippets/FaqExample.java
+   :language: java
+   :emphasize-lines: 3
+   :dedent:
+   :start-after: start myDateAsStringCodec
+   :end-before: end myDateAsStringCodec
+
+Can I make POJOs read/write directly to the field and not use the getters/setters at all?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You can configure the ``PojoCodecProvider`` to use the
+``SET_PRIVATE_FIELDS_CONVENTION``, which sets a private field through
+reflection if no public setter is available.
+
+How do I specify the collection name for a particular POJO class? Is there an annotation?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There is no annotation. We recommend adding a static string in your class as shown
+in the following code:
+
+.. code-block:: java
+
+   public class Person {
+      public static final String COLLECTION_NAME = "people";
+   }
+
+The following snippet specifies the collection name for a particular
+POJO class:
+
+.. code-block:: java
+
+   database.getCollection(Person.COLLECTION_NAME, Person.class);