odata-client

Generates java client for a service described by OData v4 metadata. Includes client libraries for Microsoft Graph primary and beta APIs, Graph Explorer API, Azure Analytics for DevOps APIs, and Microsoft Dynamics CRM. Microsoft Dynamics Finance and Operations client is in another repo.

Status : released to Maven Central

Features

• High level of type safety in generated code
• Many unit tests (real service calls are made and recorded then used for unit tests)
• Builders and method chaining for conciseness and discoverability
• Immutability! (generated objects from the model are immutable)
• OData inheritance supported for serialization and derialization
• Interschema references supported (Thompson-Reuters Datascope API uses interschema references)
• Http calls using java.net.URLConnection or using Apache HttpClient
• Collections are Iterable and streamable (via .stream())
• Paging is handled for you automatically when iterating collections
• Bound and unbound actions and functions are supported
• Custom requests supported via client._custom()
• Generated code is very clean - well formatted, no redundant imports (example)
• Microsoft Graph v1.0 client
• Microsoft Graph Beta client
• Graph Explorer client (test endpoint)
• Microsoft Analytics for DevOps 1.0, 2.0, 3.0, 4.0 and custom clients.
• Microsoft Dynamics CRM client
• Microsoft Dynamics Finance and Operations client (see https://github.com/davidmoten/microsoft-dynamics-finance-client)
• More generated clients can be added, just raise an issue
• Runs on Java 8+ (including Java 11+, 17). When running <11 the jaxb dependencies can be excluded from odata-client-runtime.

How to build

mvn clean install

Background

OData is an OASIS standard for building and consuming REST APIs. The odata-client project focuses only on OData HTTP APIs implemented using JSON payloads. A client of an OData service can be generated completely from the metadata document published by the service. An example is the Microsoft Graph Odata metadata.

The main actively supported java clients for OData 4 services are Apache Olingo and the SDL OData Framework. However, neither of these projects generate all of the code you might need. Olingo generates some code but you still have to read the metadata xml to know what you can do with the generated classes. This project odata-client generates nearly all the code you need so that you just follow auto-complete on the available methods to navigate the service.

Microsoft Graph is an OData 4 service with a Java SDK being developed at https://github.com/microsoftgraph/msgraph-sdk-java. Progress is slow and steady (but happening) on that client (8 Nov 2018) and it can do a lot already. My frustrations with the design of that client gave rise to an investigation into generating clients for OData services in general and that investigation turned into this project.

How to generate java classes for an OData service

Add odata-client-maven-plugin and build-helper-maven-plugin to your pom.xml as per odata-client-msgraph/pom.xml. You'll also need to save a copy of the service metadata (at http://SERVICE_ROOT/$metadata) to a file in your src/odata directory. Once everything is in place a build of your maven project will generate the classes and make them available as source (that's what the build-helper-maven-plugin does).

Your plugin section will look like this:

<plugin>
   <groupId>com.github.davidmoten</groupId>
   <artifactId>odata-client-maven-plugin</artifactId>
   <version>VERSION_HERE</version>
   <executions>
     <execution>
       <id>generate-odata-models</id>
       <phase>generate-sources</phase>
       <goals>
         <goal>generate</goal>
       </goals>
       <configuration>
         <metadata>src/main/odata/PATH_TO_THE_METADATA_XML_FILE</metadata>
         <schemas>
           <schema>
            <namespace>NAMESPACE_IN_YOUR_METADATA_FILE</namespace>
            <packageName>package.of.generated.classes</packageName>
           </schema>
           <!-- More schemas -->
         </schemas>
       </configuration>
     </execution>
   </executions>
</plugin>
<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>3.2.0</version>
     <executions>
      <execution>
        <id>add-source</id>
         <phase>generate-sources</phase>
         <goals>
           <goal>add-source</goal>
         </goals>
        <configuration>
          <sources>
            <source>${project.build.directory}/generated-sources/java</source>
          </sources>
        </configuration>
     </execution>
    </executions>
</plugin>

How to create a Client for your OData Service (non-Microsoft API) with Bearer Tokens.

This example considers a custom OData api available at $API_ENDPOINT that authorizes using Bearer tokens in the Authorization header. The custom api has a users list that we want to return with a call to the service. The example has a hardcoded token for simplicity.

The SchemaInfo List should contain the SchemaInfos generated for your service metadata. (See generated classes in packages ending in .schema).

    HttpClientBuilder b =
        HttpClientBuilder
            .create()
            .useSystemProperties();
            
    BearerAuthenticator authenticator =
        new BearerAuthenticator(
            () ->
                "INSERT_TOKEN_HERE",
            "$API_END_POINT");
            
    HttpService httpService =
        new ApacheHttpClientHttpService( //
            new Path(
                "$API_END_POINT",
                PathStyle.IDENTIFIERS_AS_SEGMENTS),
            b::build,
            authenticator::authenticate);
            
    final List<com.github.davidmoten.odata.client.SchemaInfo> schemaInfos =
        Arrays.asList(generate.pkg.schema.SchemaInfo.INSTANCE);
        
    Context context =
        new Context(Serializer.INSTANCE, httpService, Collections.emptyMap(), schemaInfos);

    // in this example Container is the name of the Container element in the metadata
    Container client = new Container(context);
    List<String> userEmails =
        client.users()
	.stream()
        .map(User::getEmail)
        .filter(Optional::isPresent)
        .map(x -> x.get())
        .collect(Collectors.toList());

Limitations

• Just one key (with multiple properties if desired) per entity is supported (secondary keys are ignored in terms of code generation). I've yet to come across a service that uses multiple keys but it is possible.
• see TODO

MsGraph Client

Use this dependency:

<dependency>
    <groupId>com.github.davidmoten</groupId>
    <artifactId>odata-client-msgraph</artifactId>
    <version>VERSION_HERE</version>
</dependency>

You can also use artifactId odata-client-msgraph-beta to access the beta endpoint (and they have different package names so you can use both clients in the same project if you want).

If you are running on less than Java 11 then you can exclude some dependencies but only if you are running odata-client version:

<dependency>
    <groupId>com.github.davidmoten</groupId>
    <artifactId>odata-client-msgraph</artifactId>
    <version>VERSION_HERE</version>
    <exclusions>
        <exclusion>
            <groupId>org.glassfish.jaxb</groupId>
            <artifactId>jaxb-core</artifactId>
        </exclusion>
        <exclusion>
            <groupId>org.glassfish.jaxb</groupId>
            <artifactId>jaxb-runtime</artifactId>
        </exclusion>
    </exclusions>
</dependency>

As slf4j is used for logging you may wish to exclude the slf4j-api dependency and add the slf4j logging adapter dependency (e.g. slf4j-log4j12) for your logging library:

	<exclusion>
	    <groupId>org.slf4j</groupId>
	    <artifactId>slf4j-api</artifactId>
	</exclusion>

Create a client for the Graph Explorer

There's a web test page for queries called the Graph Explorer. You can use the client against this service for experiments. Bear in mind that the Graph Explorer service doesn't support lots but it is still a good place to get a feel for it.

GraphService client = MsGraph.explorer().build();

or behind a proxy:

GraphService client = MsGraph
  .explorer()
  .proxyHost(proxyHost)
  .proxyPort(8080)
  .build();

Here's an example:

client 
  .users()
  .select("displayName")
  .stream() 
  .limit(10)
  .map(user -> user.getDisplayName().orElse("?"))
  .forEach(System.out::println);

output:

Conf Room Adams
Adele Vance
MOD Administrator
Alex Wilber
Allan Deyoung
Conf Room Baker
Ben Walters
Brian Johnson (TAILSPIN)
Christie Cline
Conf Room Crystal

Here's a contrived example with Graph Explorer that gets 5 attachment names from messages and their sizes. The example makes good use of the streaming capabilities of the odata-client API:

GraphService client = MsGraph.explorer().build();
client
  .me()
  .messages()
  .select("id")
  .stream()
  .flatMap(m -> m.getAttachments().select("name, size").stream())
  .limit(5)
  .map(a -> a.getName().orElse("?") + " " + a.getSize().orElse(-1) + "B")
  .forEach(System.out::println);

output:

analytics_icon.png 2281B
lock_circle_teal.png 2713B
collab_hero_left_2x.png 6496B
ProfileImage_320_48d31887-5fad-4d73-a9f5-3c356e68a038.png 335675B
collab_hero_right_2x.png 6611B

Create a client for Graph v1.0

The first step is to create a client that will be used for all calls in your application.

GraphService client = MsGraph 
    .tenantName(tenantName) 
    .clientId(clientId) 
    .clientSecret(clientSecret) 
    .connectTimeout(30, TimeUnit.SECONDS)
    .readTimeout(60, TimeUnit.SECONDS)
    .refreshBeforeExpiry(5, TimeUnit.MINUTES) 
    .build();

Create a client for Graph v1.0 behind a proxy

GraphService client = MsGraph 
    .tenantName(tenantName) 
    .clientId(clientId) 
    .clientSecret(clientSecret) 
    .connectTimeout(30, TimeUnit.SECONDS)
    .readTimeout(60, TimeUnit.SECONDS)
    .refreshBeforeExpiry(5, TimeUnit.MINUTES) 
    .proxyHost(proxyHost)
    .proxyPort(proxyPort)
    .proxyUsername(proxyUsername)
    .proxyPassword(proxyPassword)
    .build();

Specify the authentication endpoint

This client supports Client Credential authentication only at the moment. Raise an issue if you need a different sort.

To change the authentication endpoint used to retrieve access tokens (the default is AuthenticationEndpoint.GLOBAL):

GraphService client = MsGraph
    .tenantName(tenantName)
    .clientId(clientId)
    .clientSecret(clientSecret)
    .connectTimeout(30, TimeUnit.SECONDS)
    .readTimeout(60, TimeUnit.SECONDS)
    .refreshBeforeExpiry(5, TimeUnit.MINUTES)
    .authenticationEndpoint(AuthenticationEndpoint.GERMANY)
    .build();

If you want to do really complicated things with proxies or http in general you can use the .httpClientProvider or .httpClientBuilderExtras methods (coupled to Apache HttpClient).

Usage example 1 - simple

Here's example usage of the odata-client-msgraph artifact (model classes generated from the MsGraph metadata). Let's connect to the Graph API and list all messages in the Inbox that are unread. Note that paging is completely handled for you in the .stream() method!

String mailbox = "me";
client
    .users(mailbox) 
    .mailFolders("Inbox") 
    .messages() 
    .filter("isRead eq false") 
    .expand("attachments") 
    .stream() 
    .map(x -> x.getSubject().orElse("")) 
    .forEach(System.out::println);

Usage example 2 - more complex

Here's a more complex example which does the following:

• Counts the number of messages in the Drafts folder
• Prepares a new message
• Saves the message in the Drafts folder
• Changes the subject of the saved message
• Checks the subject has changed by reloading
• Checks the count has increased by one
• Deletes the message

MailFolderRequest drafts = client //
    .users(mailbox) //
    .mailFolders("Drafts");

// count number of messages in Drafts
long count = drafts.messages() //
    .metadataNone() //
    .stream() //
    .count(); //

// Prepare a new message
String id = UUID.randomUUID().toString().substring(0, 6);
Message m = Message
    .builderMessage() //
    .subject("hi there " + id) //
    .body(ItemBody
        .builder() //
        .content("hello there how are you") //
        .contentType(BodyType.TEXT) 
        .build()) //
    .from(Recipient
         .builder() //
         .emailAddress(EmailAddress
             .builder() //
             .address(mailbox) //
             .build())
         .build())
    .build();

// Create the draft message
Message saved = drafts.messages().post(m);

// change subject
client //
    .users(mailbox) //
    .messages(saved.getId().get()) //
    .patch(saved.withSubject("new subject " + id));

// check the subject has changed by reloading the message
String amendedSubject = drafts //
    .messages(saved.getId().get()) //
    .get() //
    .getSubject() //
    .get();
if (!("new subject " + id).equals(amendedSubject)) {
    throw new RuntimeException("subject not amended");
}

long count2 = drafts //
    .messages() //
    .metadataNone() //
    .stream() //
    .count(); //
if (count2 != count + 1) {
    throw new RuntimeException("unexpected count");
}

// Delete the draft message
drafts //
    .messages(saved.getId().get()) //
    .delete();

Collections and paging

odata-client handles the annoying paging stuff under the covers so you don't have to worry about it. Let's look at some examples.

We'll get the list of users:

List<User> users = client.users().toList();

That was easy wasn't it! Under the covers odata-client kept calling pages (using @odata.nextLink) and building the list to return. This won't always be a good idea because the Collection might be very big and you might not want all the data anyway. What are some alternatives?

client.users() is itself an Iterable so you can do this:

for (User user: client.users()) 
  System.out.println(user);

or

Iterator<User> it = client.users().iterator();
while (it.hasNext()) 
  System.out.println(it.next());

You can use .stream():

client.users()
  .stream() 
  .forEach(System.out::println);

Again, all paging is taking care of. When the current page runs out the library requests another one.

If you do want to do explicit paging then you can do this:

CollectionPage<User> users = client.users().get();

CollectionPage has methods currentPage and nextPage.

Your own page size

You can request a different page size than the default via a special HTTP request header but the server may choose to ignore your request:

List<User> users = client.users().maxPageSize(200).get().currentPage();

So what if you want to receive the collection in custom size pages regardless of the page size being delivered by the server? odata-client has two utility methods to help you out. Let's chop the stream of User into pages of 15 elements:

import com.github.davidmoten.odata.client.Util;

Iterator<List<User>> it = Util.buffer(client.users().iterator(), 15);

or with streams:

Stream<List<User>> users = Util.buffer(client.users().stream(), 15);

Getting a collection from a link

Some users need stateless paging so want to recommence the next page from the odata.nextLink value in the page json. Here's an example:

String nextLink = "https://...";
List<User> users = client
  .users()
  .urlOverride(nextLink)
  .get()
  .currentPage();

Getting json for the collection

Some users want to do a passthrough of Graph API responses in JSON format through to their clients. You can obtain a simplified collection page response as JSON like this:

CollectionPage<User> page = client.users().get();
String json = page.toJsonMinimal();

Filtering a collection by type

To only return items of a certain type from a collection request (this is called "restriction to instances of the derived type" in the OData specification):

client
  .directoryObjects()
  .filter(User.class)
  .forEach(System.out::println);

Updating Microsoft Graph metadata

Developer instructions:

cd odata-client-msgraph
./update-metadata.sh
cd ..
## check if still builds!
mvn clean install

Note that the latest metadata is downloaded from microsoft but that also:

• HasStream="true" is added to EntityType itemAttachment
• HasStream="true" is added to EntityType message

URLs are:

• https://graph.microsoft.com/v1.0/$metadata
• https://graph.microsoft.com/beta/$metadata

Timeouts

Connect and read timeouts can be specified when creating the client and apply globally:

GraphService client = MsGraph
    .tenantName(tenantName)
    .clientId(clientId)
    .clientSecret(clientSecret)
    .connectTimeout(30, TimeUnit.SECONDS)
    .readTimeout(60, TimeUnit.SECONDS)
    .refreshBeforeExpiry(5, TimeUnit.MINUTES)
    .authenticationEndpoint(AuthenticationEndpoint.GERMANY)
    .build();

Global timeouts can be overriden by request:

List<User> users = client
  .users()
  .connectTimeout(10, TimeUnit.SECONDS)
  .readTimeout(30, Timeout.SECONDS)
  .toList();

Download an email in SMTP MIME format

Use Message.getStream().

Here's an example using Graph Explorer where we download the MIME format of a random email returned by the service (you can run this exact code yourself to test):

GraphService client = MsGraph.explorer().build();
String mimeMessage = 
  client
    .me()
    .messages()
    .stream()
    .findFirst()
    .get()
    .getStream()
    .get()
    .getStringUtf8();
System.out.println(mimeMessage);

Output:

From: Sundar Ganesan <[email protected]>
To: Megan Bowen <[email protected]>, Alex Wilber
Subject:
Thread-Index: AQHWhnph+xDTvdQDAJzfEoyf/g4tCA==
X-MS-Exchange-MessageSentRepresentingType: 1
Date: Wed, 9 Sep 2020 07:25:22 +0000
Message-ID: 1599636322761
Content-Language: en-US
X-MS-Exchange-Organization-SupervisoryReview-TeamsContext:
	{"SenderId":"19806f8c015344149305dc48012b4789","AadGroupId":null,"ThreadId":"19:[email protected]","MessageId":1599636322761,"ParentMessageId":null,"TenantId":"91c1bcb4-2349-4abd-83c1-6ae4ffaf7f6c","ThreadType":"chat","CorrelationVector":"KuDTOICw9UWVpDHto11XFw.1.1.1.2441281688.1.0"}
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
X-MS-Exchange-Organization-RecordReviewCfmType: 0
Content-Type: multipart/alternative; boundary="_000_1599636322761_"
MIME-Version: 1.0

--_000_1599636322761_
Content-Type: text/plain; charset="us-ascii"

test

--_000_1599636322761_
Content-Type: text/html; charset="us-ascii"

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
</head>
<body>
test
</body>
</html>

--_000_1599636322761_--

Sending an email with an attachment

Unfortunately sending an email with an attachment is complicated somewhat by Microsoft Graph forcing users to use two different methods to upload an attachment depending on the size of the attachment. Default maximum size for an attachment is apparently 25MB according to Microsoft docs though an administrator can increase the limit up to 150MB if required.

To help send an email a helper utility class called Email exists. Here's an example that sends an email with two attachments:

Email
  .mailbox(mailbox) 
  .subject("hi there " + new Date())
  .bodyType(BodyType.TEXT)
  .body("hello there how are you")
  .to("[email protected]")
  .header("x-security-classification", "OFFICIAL")
  .attachment(file)
  .name("list.txt")
  .contentMimeType("text/plain")
  .chunkSize(512 * 1024)
  .attachment("hi there")
  .name("greeting.txt")
  .contentMimeType("text/plain")
  .send(client);

The builder code above does quite a lot for you. For reference here's how you do it using the generated classes only:

GraphService client = ...;
File file = ...;
String contentType = "text/plain";
String mailbox = "[email protected]";

// create new outbound mail in Drafts folder
MailFolderRequest drafts = client //
    .users(mailbox) //
    .mailFolders("Drafts");
Message m = Message.builderMessage() //
    .subject("hi there " + new Date()) //
    .body(ItemBody.builder() //
            .content("hello there how are you") //
            .contentType(BodyType.TEXT).build()) //
    .from(Recipient.builder() //
            .emailAddress(EmailAddress.builder() //
                    .address(mailbox) //
                    .build()) //
            .build()) //
    .toRecipients(Recipient.builder() //
            .emailAddress(EmailAddress.builder() //
                    .address("[email protected]") //
                    .build()) //
            .build()) //
    .build();

m = drafts.messages().post(m);

// Upload attachment to the new mail
// We use different methods depending on the size of the attachment
// because will fail if doesn't match the right size window
if (file.length() < 3000000) {
    client.users(mailbox) //
        .messages(m.getId().get()) //
        .attachments() //
        .post(FileAttachment.builderFileAttachment() //
           .name(file.getName()) //
           .contentBytes(Files.readAllBytes(file.toPath())) //
           .contentType(contentType).build());
} else {
    AttachmentItem a = AttachmentItem //
        .builder() //
        .attachmentType(AttachmentType.FILE) //
        .contentType(contentType) //
        .name(file.getName()) //
        .size(file.length()) //
        .build();
    
    int chunkSize = 500*1024;
    client //
        .users(mailbox) //
        .messages(m.getId().get()) //
        .attachments() //
        .createUploadSession(a) //
        .get() //
        .putChunked() //
        .readTimeout(10, TimeUnit.MINUTES) //
        .upload(file, chunkSize, Retries.builder().maxRetries(2).build());
}

// send the email 
// you can't just use m.send().call() because Graph doesn't 
// honour the path corresponding to m for send method and throws
// a 405 status code
client
  .users(mailbox)
  .messages(m.getId().get())
  .send()
  .call();

Delta collections

Some functions return delta collections which track changes to resource collections. In the Graph API v1.0 there are delta functions on users, calendar events, and messages.

Here's an example of usage:

// get a delta that returns no users but marks where future deltas will be based on
CollectionPage<User> delta = client.users().delta().deltaTokenLatest().get();

// a while later
delta = delta.nextDelta().get();

// delta is a CollectionPage and can be iterated upon or paged through as you like
// if you don't iterate through the collection the next call to 
// nextDelta() will do it for you because the deltaLink is on the last page 
// of the current collection 

// print out all users that have changed
delta.forEach(System.out::println);

// a while later
delta = delta.nextDelta().get();
...

A special streaming method is available also that returns a list of wrapped delta objects then the delta link to use for the next delta call:

Stream<ObjectOrDeltaLink<User>> delta = 
    client
      .users()
      .delta()
      .get()
      .streamWithDeltaLink();

Using the delta link from the last element of the stream the next delta call can be made like so:

Stream<ObjectOrDeltaLink<User>> delta = 
    client 
      .users()
      .overrideUrl(deltaLink)
      .get()
      .streamWithDeltaLink();

ObjectOrDeltaLink is serializable to JSON via its Jackson annotations and at least one user is using the streamWithDeltaLink method to pass large deltas over a network via WebFlux (see issue #44).

Expand

Special support is provided for the $expand option. Here's an example:

Attachment attachment = client
  .users(emailId)
  .mailFolders(folderId)
  .messages(messageId)
  .attachments(attachmentId)
  .expand("microsoft.graph.itemattachment/item")
  .get();
if (attachment instanceof ItemAttachment) {
    ItemAttachment a = (ItemAttachment) attachment;
    OutlookItem item = a.getItem().get();
    ...
}

When the above code is called, the line OutlookItem item = a.getItem().get() will not actually make a network call but rather use the json in unmapped fields of attachment. If the json is not present in the unmapped fields then a network call will be made.

This support is present for both Entity requests and Enitty Collection requests.

Logging

The default http client Apache httpclient uses Apache Commons Logging and the odata-client libraries use slf4j. To get full access to all logs you'll need to ensure that the right adapters are present that pipe logs to your preferred logging library. Tests in odata-client-msgraph demonstrate the use of log4j as the preferred logger. You'll note that these dependencies are present:

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>jcl-over-slf4j</artifactId>
    <version>${slf4j.version}</version>
</dependency>

 <dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-slf4j-impl</artifactId>
    <version>${log4j.version}</version>
</dependency>

A configuration file for log4j is also present (in src/test/resources but you might want it in src/main/resources):

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="INFO">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>

If you want DEBUG logging just set the Root level to DEBUG.

Serialization

odata-client generated classes are annotated with Jackson JSON annotations specifically to support internal serialization and deserialization for communication with the service. Since 0.1.20 entities are annotated with @JsonInclude(Include.NON_NULL) so that default serialization with Jackson will exclude null values (internally this annotation is overriden for certain use cases such as when we want tell the service to update a field to null).

Custom requests

To get more precise control over the interaction with an OData api you can use the methods of CustomRequest. Here's an example that posts json to the service and recieves a json response:

CustomRequest c = client._custom().withRelativeUrls();
String json = c.getString("me/mailFolders/inbox/messages?$select=id&count=true", RequestOptions.EMPTY, RequestHeader.ODATA_VERSION);
System.out.println(json);

Output:

{
	"@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users('48d31887-5fad-4d73-a9f5-3c356e68a038')/mailFolders('inbox')/messages(id)",
	"@odata.count": 21,
	"@odata.nextLink": "https://graph.microsoft.com/v1.0/me/mailFolders/inbox/messages?$select=id&count=true&$skip=10",
	"value": [
		{
			"@odata.etag": "W/\"CQAAABYAAAAiIsqMbYjsT5e/T7KzowPTAAL0pwit\"",
			"id": "AAMkAGVmMDEzMTM4LTZmYWUtNDdkNC1hMDZiLTU1OGY5OTZhYmY4OABGAAAAAAAiQ8W967B7TKBjgx9rVEURBwAiIsqMbYjsT5e-T7KzowPTAAAAAAEMAAAiIsqMbYjsT5e-T7KzowPTAAL0sBcuAAA="
		},
                ...
	]
}

Usage Notes

Streams

To find the read url for a property that is of type Edm.Stream you generally need to read the entity containing the stream property with the Accept: odata.metadata=full request header (set .metadataFull() before calling get() on an entity). As of 0.1.54 this request header is the default for Media Entities or entities with stream properties (but not for collections of these entities).

Implementation Notes

Generator

Some of the metadata access patterns are O(N²) in the generator but does not appear to be significant. If you think it is then the library can start using maps for lookups.

HasStream

Suppose Person has a Navigation Property of Photo then using the TripPin service example, calling HTTP GET of

https://services.odata.org/V4/(S(itwk4e1fqfe4tchtlieb5rhb))/TripPinServiceRW/People('russellwhyte')/Photo

returns:

{
"@odata.context": "http://services.odata.org/V4/(S(itwk4e1fqfe4tchtlieb5rhb))/TripPinServiceRW/$metadata#Photos/$entity",
"@odata.id": "http://services.odata.org/V4/(S(itwk4e1fqfe4tchtlieb5rhb))/TripPinServiceRW/Photos(2)",
"@odata.editLink": "http://services.odata.org/V4/(S(itwk4e1fqfe4tchtlieb5rhb))/TripPinServiceRW/Photos(2)",
"@odata.mediaContentType": "image/jpeg",
"@odata.mediaEtag": "W/\"08D6394B7BA10B11\"",
"Id": 2,
"Name": "My Photo 2"
}

We then grab the @odata.editLink url and call that with /$value on the end to GET the photo bytes:

https://services.odata.org/V4/(S(itwk4e1fqfe4tchtlieb5rhb))/TripPinServiceRW/Photos(2)/$value

Generated classes, final fields and setting via constructors

The initial design for setting fields was via constructors with final fields but Msgraph Beta service goes for gold on the number of fields and well exceeds the JVM limit of 256 with the Windows10GeneralConfiguration entity. As a consequence we have private theoretically mutable fields and a protected no-arg constructor. In practice though the fields are not mutable as the only creation access is through a builder() or with*(...) which return new instances.

PATCH support

If choosing the JVM Http client (via HttpURLConnection) then the HTTP verb PATCH is not supported. However, if using this client and a ProtocolException is thrown then the client attempts the call using the special request header X-HTTP-Override-Method and the verb POST. The detection of the ProtocolException is cached and future PATCH calls will then use the alternative methods (for the runtime life of the application).

TODO

• support OpenType (arbitrary extra fields get written)
• support EntityContainer inheritance (maybe, no sample that I've found uses it so far)
• support precision, scale (maybe)
• more decoupling of model from presentation in generation
• use annotations (docs) in javadoc
• support function composition
• support count
• support raw
• support $ref
• support updating/creating streams
• support geographical primitive types (where's the spec?!!)
• support references to other metadata files (imports)
• auto-rerequest with odata.metadata=full header if Edm.Stream is read
• support TypeDefinition
• only generate classes that are actually used (e.g. not every Entity or ComplexType needs a corresponding Collection request)
• remove context property "modify.stream.edit.link" from MsGraph client once they support their own @odata.mediaEditLink!
• add helper methods to generated UploadUrl class in MsGraph
• add optional retry logic to StreamUploaderChunked
• increase chunked upload efficiency by writing read bytes to destination immediately, retaining the ability to retry the chunk