Part 2: MicroProfile Meeting Application - Adding Persistence
Overview
This lab takes you through how to update the MicroProfile Meeting application to add persistence.
At the time this lab was written MicroProfile had not defined a persistence mechanism. This is not because MicroProfile does not view persistence as important, but indicates the many equally valid choices that could be made for persistence in microservices. In this lab, Cloudant is used but there are other equally valid options like JPA, MongoDB, or Cassandra.
Adapted from the blog post: Writing a simple MicroProfile application: Adding persistence
Prerequisites
-
Completed Part 1: MicroProfile Meeting Application
-
Eclipse IDE for Web Developers: Run the installer and select Eclipse IDE for Java EE developers. Note: these steps were tested on the 2018-09 version of Eclipse running on Linux and Liberty Developer Tools 18.0.0.3. Note: If you encounter an error message like
Could not initialize class org.codehaus.plexus.archiver.jar.JarArchiver
please see the Troubleshooting section. -
IBM Liberty Developer Tools (WDT)
- Start Eclipse
- Launch the Eclipse Marketplace: Help -> Eclipse Marketplace
- Search for IBM Liberty Developer Tools, and click Install with the defaults configuration selected
-
Install the IBM Cloud CLI
Steps
Step 1. Check out the source code
From the command line
Run the following commands:
$ git clone https://github.com/IBM/microprofile-meeting-persistence.git
In Eclipse, import the project as an existing project.
- In Eclipse, switch to the Git perspective.
- Click Clone a Git repository from the Git Repositories view.
- Enter URI
https://github.com/IBM/microprofile-meeting-persistence.git
- Click Next, then click Next again accepting the defaults.
- From the Initial branch drop-down list, click master.
- Select Import all existing Eclipse projects after clone finishes, then click Finish.
- Switch to the Java EE perspective.
- The meetings project is automatically created in the Project Explorer view.
Step 2. Installing MongoDB
If you completed the previous labs and installed MongoDB, make sure MongoDB is running. If you are starting fresh, make sure you install MongoDB. Depending on what platform you are on the installation instructions may be different. For this exercise you should get the community version of MongoDB from the mongoDB download-center.
- Once installed you can run the MongoDB database daemon using:
mongod -dbpath <path to database>
The database needs to be running for the application to work. If it is not running there will be a lot of noise in the server logs.
Step 3. Update application to compile against MongoDB API
To start writing code, the Maven pom.xml needs to be updated to indicate the dependency on MongoDB:
- Open the
pom.xml
. - On the editor select the Dependencies tab.
- On the Dependencies tab there are two sections, one for Dependencies, and the other for Dependency Management. Just to the right of the Dependencies box there is a Add button. Click the Add button.
- Enter a groupdId of
org.mongodb
. - Enter a artifactId of
mongo-java-driver
. - Enter a version of
2.14.3
. - In the scope drop-down, select provided. This will allow the application to compile, but will prevent the Maven WAR packager putting the API in the WAR file. Later the build will be configured to make it available to the server.
- Click OK.
- Save the
pom.xml
.
Step 4. Update MeetingsUtil to convert between MongoDB and JSON-Processing objects
When updating the application, we need to convert between the MongoDB representation of data and the JSON-Processing one. Rather than scatter this around this can be placed in the MeetingsUtil class:
-
Open the
MeetingsUtil
class from meetings > Java Resources > src/main/java > net.wasdev.samples.microProfile.meetings > MeetingsUtil.java -
The first method that is needed takes a MongoDB
DBObject
and returns aJsonObject
. At the beginning of the file, after the class definition, add the method declaration:
public static JsonObject meetingAsJsonObject(DBObject obj) {
// method body will go here
}
- This introduces one new class, the
DBObject
class is in thecom.mongodb
package:
import com.mongodb.DBObject;
- The first step in creating a new
JsonObject
is to create aJsonObjectBuilder
using theJSON
class. All of these are already used in the class so no new imports will be required. Add the following line to the start of the method:
public static JsonObject meetingAsJsonObject(DBObject obj) {
JsonObjectBuilder builder = Json.createObjectBuilder();
- The JSON object for a meeting uses a field called
id
. MongoDB uses_id
for the same function, soid
in JSON will map to_id
in MongoDB. To extract theid
field from theDBObject
and add it to the JSON, add this line to the method:
builder.add("id", (String) obj.get("_id"));
- The
title
field can be directly mapped from JSON to the MongoDB object. Thetitle
is a String but, to ensure the right add method is called, cast it to a String. Add this line:
builder.add("title", (String) obj.get("title"));
- The
duration
field is a Long. As before it needs to be cast to a Long to ensure the rightadd
method is called:
builder.add("duration", (Long) obj.get("duration"));
- If a meeting is running it’ll have a
meetingURL
field. If it isn’t running it’ll return null. If there is nomeetingUR
L field, we don’t want to add it to the meeting returned so we want to only add ifmeetingURL
is non-null. Add this:
String meetingURL = (String) obj.get("meetingURL");
if (meetingURL != null)
builder.add("meetingURL", meetingURL);
- Finally we need to return a
JsonObject
. This can be obtained by calling thebuild
method on theJsonObjectBuilder
. Add this:
return builder.build();
- Next, we need a method that does the opposite, mapping from a
JsonObject
to aDBObject
. This method serves two purposes: It creates a newDBObject
and it merges aJsonObject
to an existingDBObject
, so that it has two parameters rather than one. After the end of the previous method add this:
public static DBObject meetingAsMongo(JsonObject json, DBObject mongo) {
// method body will go here
}
- The first thing to do in this new method is check if the
DBObject
passed in is null. If it is null, a newDBObject
is created.DBObject
is abstract so aBasicDBObject
is what will be instantiated. At the beginning of the method add this (there will be a compile error after this but don’t worry, it’ll be fixed soon):
if (mongo == null) {
mongo = new BasicDBObject();
- Next, the
id
needs to be moved from theJsonObject
to the newDBObject
. This should only be done when a newDBObject
is created because, otherwise, a disconnect between theURL
and theJsonObject
could result in anid
being incorrectly overwritten. Add this:
mongo.put("_id", json.getString("id"));
}
- This introduced a new class, the
BasicDBObject
which is in thecom.mongodb
package but needs to be imported:
import com.mongodb.BasicDBObject;
- The
title
field is a direct mapping from theJsonObject
to theDBObject
but theJsonObject
contains aJsonString
which needs to be converted to a String. ThetoString
method can’t be used for this because it wraps the String literal with quotes, which isn’t required here. FortunatelyJsonObject
provides a convenientgetString
method for this:
mongo.put("title", json.getString("title"));
- The
duration
field is also a direct mapping but it’s aJsonNumber
in theJsonObject
, which needs to be converted to a Long to go into theDBObject
:
mongo.put("duration", ((JsonNumber) json.get("duration")).longValue());
- This introduced the
JsonNumber
, which needs to be imported:
import javax.json.JsonNumber;
- We want to get the
meetingURL
but, since it might not be there, you can’t use thegetString
method because it’ll throw aNullPointerException
if there is no field with that name. To get around this, use theget
method, which returns aJsonString
. A null check can then be performed and only if it is non-null will it be added to the JSON. ThegetString
method must be used since toString wraps the string in quotes:
JsonString jsonString = json.getJsonString("meetingURL");
if (jsonString != null) {
mongo.put("meetingURL", jsonString.getString());
}
- This introduced the
jsonString
, which needs to be imported:
import javax.json.JsonString;
- Finally return the mongo object and save the file.
return mongo;
Step 5. Updating the MeetingManager
The MeetingManager
currently makes use of a ConcurrentMap
to store the meetings. All the code that integrates with this needs to be updated. In this section this is done one step at a time; as a result there will be compilation errors until you get to the end:
-
Open the
MeetingManager
class from meetings > Java Resources > src/main/java > net.wasdev.samples.microProfile.meetings > MeetingManager.java. -
After the class definition delete the following line from the file:
private ConcurrentMap<String, JsonObject> meetings = new ConcurrentHashMap<>();
- To interact with MongoDB, an instance of
DB
needs to be injected. This can be done using the@Resource
annotation which can identify which resource fromJNDI
to inject. Add the code where theConcurrentMap
was removed (in the previous step):
@Resource(name="mongo/sampledb")
private DB meetings;
- This pulls in two new classes. The MongoDB
DB
class and the Java EE@Resource
annotation. These need to be imported:
import javax.annotation.Resource;
import com.mongodb.DB;
- MongoDB stores entries in a collection in the database. The first thing to do when writing or reading is to select the collection. To simplify code later on, let’s create a convenience method to get the collection:
public DBCollection getColl() {
return meetings.getCollection("meetings");
}
- This introduces a new class, the
DBCollection
class, which is in the com.mongodb package. This needs to be imported:
import com.mongodb.DBCollection;
- Find and edit the
add
method:
- Remove the method body from the
add
method. This will be replaced to update the database.
public void add(JsonObject meeting) {
// code will be added here
}
- First get the collection.
DBCollection coll = getColl();
- The method is given a
JsonObject
and we need aDBObject
for MongoDB, so we need to convert. The API can take an existing entry from the database, so first lets see if we can find something from the database using the findOne method:
DBObject existing = coll.findOne(meeting.getString("id"));
- This introduces a new class, the
DBObject
class which is in thecom.mongodb
package. This needs to be imported:
import com.mongodb.DBObject;
- Next call the
MeetingsUtil
convenience method to convert fromJsonObject
toDBObject
:
DBObject obj = MeetingsUtil.meetingAsMongo(meeting, existing);
- Finally save the new or changed
DBObject
back into the database:
coll.save(obj);
- Find and update the
get
method:
- Remove the method body from the
get
method (this will be replaced to fetch from the database):
public JsonObject get(String id) {
// code will be added here
}
- To get a single entry the collection needs to be obtained, an entry found by id, and then converted to a
JsonObject
using the utility method created earlier. Add the following line to theget
method:
return MeetingsUtil.meetingAsJsonObject(getColl().findOne(id));
- Find and update the
list
method. Thelist
method is slightly more complicated to update. The general structure stays the same but for loop will change. To iterate over entries in a collection aDBCursor
is used and that returns aDBObject
. TheDBObject
then needs to be converted to aJsonObject
. Replace the existing loop that looks like this:
for (JsonObject meeting : meetings.values()) {
results.add(meeting);
}
with this one
for (DBObject meeting : getColl().find()) {
results.add(MeetingsUtil.meetingAsJsonObject(meeting));
}
- Find and update the
startMeeting
method:
- This change will radically simplify the code because there is no need to create and merge multiple
JsonObject
s. Instead, you can simply add themeetingURL
to the existingDBObjec
t. Theid
andurl
will still need to be fetched from theJsonObject
. Remove the following lines from thestartMeeting
method:
JsonObject existingMeeting = meetings.get(id);
JsonObject updatedMeeting = MeetingsUtil.createJsonFrom(existingMeeting).add("meetingURL", url).build();
meetings.replace(id, existingMeeting, updatedMeeting);
- After the
id
andurl
are fetched, replace the removed code with the following four lines to get a collection, find the meeting entry, set themeetingURL
, and then save it back to the database:
DBCollection coll = getColl();
DBObject obj = coll.findOne(id);
obj.put("meetingURL", url);
coll.save(obj);
- Save the file.
The MeetingManager
is now able to persist to a MongoDB database and back. However, the server still needs to be configured to enable it. This consists of two parts: First, server configuration and, second, getting the server runtime set up.
Step 6. Updating the Server Configuration
The server configuration is part of the project so first let’s configure that:
-
Open the
server.xml
from src > main > liberty > config > server.xml. -
Add
mongodb-2.0
as a new feature. It should look like this:
<featureManager>
<feature>microProfile-2.0</feature>
<feature>mongodb-2.0</feature>
</featureManager>
- A shared library needs to be defined to be used by the application and the runtime for defining the MongoDB resources:
<library id="mongodriver">
<file name="${shared.resource.dir}/mongo-java-driver.jar"/>
</library>
- Next the
mongo
needs to be defined. This tells the server where themongo
server instance is running:
<mongo id="mongo" libraryRef="mongodriver">
<ports>27017</ports>
<hostNames>localhost</hostNames>
</mongo>
- Next, define the database:
<mongoDB databaseName="meetings" jndiName="mongo/sampledb" mongoRef="mongo"/>
- Finally, configure the application so it can see the MongoDB classes:
<webApplication location="meetings-${project.version}.war">
<classloader commonLibraryRef="mongodriver"/>
</webApplication>
- Save the file.
The next step is to configure the Maven build to make sure all the resources end up in the right place.
Step 7. Updating the Maven POM
The Maven POM needs to be updated to do a few things: It needs to copy the MongoDB Java driver into the Liberty server, define an additional bootstrap property, copy the application to a different location, and ensure that the mongodb-2.0
feature is installed:
-
Open the
pom.xml
in the root of the project. -
Select the
pom.xml
tab in the editor.
Copy the MongoDB Java driver
- Search the file for the string
maven-dependency-plugin
you should see this in the file:
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.10</version>
<executions>
<execution>
<id>copy-server-files</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<includeArtifactIds>server-snippet</includeArtifactIds>
<prependGroupId>true</prependGroupId>
<outputDirectory>${project.build.directory}/wlp/usr/servers/${wlpServerName}/configDropins/defaults</outputDirectory>
</configuration>
</execution>
</executions>
This is copying server snippets from dependencies into the server configuration directory. We are going to add to it instructions to download the mongo-java-driver
, copy it to the usr/shared/resources
folder, and strip the version off the JAR file name. This last part means we don’t have to remember to update the server.xml
every time the dependency version is upgraded.
- To add these additional instructions, add the following lines after the
</execution>
closing tag:
<execution>
<id>copy-mongodb-dependency</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<includeArtifactIds>mongo-java-driver</includeArtifactIds>
<outputDirectory>${project.build.directory}/wlp/usr/shared/resources/</outputDirectory>
<stripVersion>true</stripVersion>
</configuration>
</execution>
project.version
into bootstrap.properties
Place The server.xml
references the WAR by artifact name and version. The version is referenced using a variable which needs to be provided to the server. This can easily be done using the bootstrap.properties
:
- Search the
pom.xml
file for the string<bootstrapProperties>
. You should see this in the file:
<bootstrapProperties>
<default.http.port>${testServerHttpPort}</default.http.port>
<default.https.port>${testServerHttpsPort}</default.https.port>
</bootstrapProperties>
- Before the closing add the following line:
<project.version>${project.version}</project.version>
apps
folder
Copy the application to the The Maven POM deploys the application into the dropins
folder of the Liberty server but this doesn’t allow a shared library to be used. So, instead, the application needs to be copied to the apps
folder:
- Search in the
pom.xml
for the stringdropins
, you should see this:
<goals>
<goal>copy-resources</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/wlp/usr/servers/${wlpServerName}/dropins</outputDirectory>
- Update the word dropins to be apps. It should look like this:
<configuration>
<outputDirectory>${project.build.directory}/wlp/usr/servers/${wlpServerName}/apps</outputDirectory>
mongodb-2.0
feature from the Liberty repository
Install the The mongodb-2.0
feature is not in the Liberty server installations that are stored in the Maven repository so it needs to be downloaded from the Liberty repository at build time:
- Search the
pom.xml
for the stringpackage-server
, you should see this:
<execution>
<id>package-app</id>
<phase>package</phase>
<goals>
<goal>package-server</goal>
</goals>
</execution>
</executions>
- Just before the
</executions>
tag, add the following lines to cause themongodb-2.0
feature to be installed:
<execution>
<id>install-feature</id>
<phase>package</phase>
<goals>
<goal>install-feature</goal>
</goals>
<configuration>
<features>
<acceptLicense>true</acceptLicense>
<feature>mongodb-2.0</feature>
</features>
</configuration>
</execution>
- Save the
pom.xml
.
Step 8. Running the application
Eclipse WDT
There are two ways to get the application running from within WDT:
- The first is to use Maven to build and run the project:
- Run the Maven
install
goal to build and test the project: Right-click pom.xml in themeetings
project, click Run As… > Maven Build…, then in the Goals field typeinstall
and click Run. The first time you run this goal, it might take a few minutes to download the Liberty dependencies. - Run a Maven build for the
liberty:start-server goal
: Right-click pom.xml, click Run As… > Maven Build, then in the Goals field, typeliberty:start-server
and click Run. This starts the server in the background. - Open the application, which is available at
http://localhost:9080/meetings/
. - To stop the server again, run the
liberty:stop-server
build goal.
- The second way is to right-click the
meetings
project and select Run As… > Run on Server but there are a few things to note if you do this. WDT doesn’t automatically add the MicroProfile features as you would expect so you need to manually add those. Also, any changes to the configuration insrc/main/liberty/config
won’t be picked up unless you add an include.
Find out more about MicroProfile and WebSphere Liberty.
IBM Cloud
You can run your application on IBM Cloud using Cloud Foundry.
- Login to your IBM cloud account
ibmcloud cf login
- Push your application to IBM Cloud (specifying no start)
$ ibmcloud cf push --no-start <yourappname> -p wlp/usr/servers/meetingsServer
-
While your app is deploying, create a Compose MongoDB instance on IBM Cloud. Name the service instance
mongo/sampledb
, leave all other default configurations. Click Create. -
From your IBM Cloud Dashboard, find your deployed app and click on it.
-
On the left-hand side, click Connections. Then click Connect existing.
-
Find your
mongo/sampledb
and click on it. It will prompt you to restage the app, click Restage. -
Once the app finishes restaging, you can revisit the route/url. Be sure to add
/meetings
to the end of the route to hit the home page of your app.
Next Steps
Part 3: MicroProfile Application - Using Java EE Concurrency