Category Archives: springframework

Spring Migration Analyzer – The Beginning

Spring Team surprised us once again with Spring Migration Analyzer tool. Migration with Spring wasn’t so painful, BUT this one create report for us. Now it easier to estimate effort and we now spots where we should put our attention.

I read InfoQ article: “Spring Migration Analyzer: An Assistant For JavaEE To Spring Conversion” about great features and possibilities, but I rather do not belief until I touch :).

Now guys have a lot to do but in some point SMA should be able to run just on sources (especially if this is ant, ivy, maven or gradle project).

I ran this tool in this projects:

  1. open source project (war – 30Mb) with spring 3.1, guava, hibernate – nothing fancy
    • First run: java.lang.OutOfMemoryError: Java heap space -> so I add more heap, and rerun.
    • Second run (512M) – “Poller SunPKCS11-Darwin” java.lang.OutOfMemoryError: Java heap space -> so I found SMA-21 – fix in M2 – let’s switch do suggested nightly build
    • While third build was running I checked M2 fixes – so my advice is use nightly build.
    • Third run (1Gb – nighty) : 1m10.842s (real):  Nothing special, and a lot of false positives, as example the migrator assumes that I handle transaction programmatically because in org.springframework.transaction.jta.ManagedTransactionAdapter I’m using void public commit() and that is quite opposite ;).
    • OK – let assume it will work better when, there is no spring yet.
  2. some secret project (zip 10Mb) guice no j2ee, no spring at all.
    • First run : 0m14.807s : look promising.
    • Two findings
      • The application utilises the JMS API. Typically, little or no migration is required as JMS can be used within Tomcat. During the migration, it may be worth considering using Spring’s JMS support, for example JmsTemplate, to simplify the code.
      • The application utilises the JNDI API. JNDI is available in Tomcat and therefore no work is required to migrate the application. However, it may be worth considering using Spring’s <jee-jndi-lookup> support to perform any JNDI lookups, rather than using the JNDI API directly.
    • BUT grep -rial “jms” src/  -> nothing same for jndi
    • Fail once again

I’ve skipped checking another one, as the project started, there is no point to kick the Younglings

They’are just started (SMA-24 do not exists) and  from my point of view it might be a good tool in the future: My ideas are:

  • automatic exclusion on common names: eg. org.springframework
  • working with source code
  • understanding dependencies (most java project are managed by ivy,maven,gradle)

Anyway, it worth to now that such tool as Spring Migration Analyzer is rising, or now it is the best time to join and help a little bit:

Spring Template Objects Testing

My friend asked me, how we should test this piece of code

public void fire(final NotificationMessage message) {
  jmsTemplate.send(new MessageCreator() {
    @Override
    public Message createMessage(Session session) throws JMSException {
      return session.createObjectMessage(message);
    }
  });
}

Mock, stubs, arguments matchers are not successful here. Of course we can mock jmsTemplate, verify if send method was executed, but this way we only test if springframework works properly. Should we leave this to integration test?

Of course not, and our business part is: session.createObjectMessage(message). We have to change our code. First at all we provide second method.

public void fire(final NotificationMessage message) {
  this.fire(message, getMessageCreator(message));
}
public|protected| void fire(final NotificationMessage message, MessageCreator mc) {
  jmsTemplate.send(mc);
}

This two methods are easily testable by using mocks and verifying object interactions. We can decide about method modifier:

  • public – if we want second function to be available in our API.
  • protected – for future subclass usage.
  • package public – for use in package.
  • or even private

Finally we have decide about getMessageCreator(message).

  1. Provide Factory Method for it: MessageCrator getMessageCreator(NotificationMessage message);
    MessageCreator getMessageCreator(final NotificationMessage message) {
      return new MessageCreator() {
        @Override
        public Message createMessage(Session session) throws JMSException {
          return session.createObjectMessage(message);
        }
      };
    }
    
  2. Create Class which implements MessageCreator interface
    public class NotificationMessageCreator implements MessageCreator {
        private final NotificationMessage message;
    
        public NotificationMessageCreator(NotificationMessage message) {
            this.message = message;
        }
        @Override
        public Message createMessage(Session session) throws JMSException {
            return session.createObjectMessage(message);
        }
    }
    

I think both approaches are ok, so choose better one for you.

Of course you may argue that you don’t need unit test, you will have integration test for that part of the code. Unfortunately integration tests are slow and from time to time they fail, so for simple check I prefer unit test.

Summary

We use a lot of Spring Template Object helpers, and most of the time we are tempted to create anonymous class in place. This way we make our code hard to unit test. Consider this approach to make your code easier to test and maintain. What do you think about that?


Spring Data – Redis – tutorial

Spring Data project provides a solution to access data stored in new emerging technologies like NoSQL databases, cloud based services etc. When we look into SpringSource git repository we see a lot of spring-data projects:

  • spring-data-commons: common interfaces and utility class for other spring-data projects.
  • spring-data-column: support for column based databases. It has not started yet, but there will be support for Cassandra and HBase
  • spring-data-document: support for document databases. Currently MongoDB and CouchDB are supported.
  • spring-data-graph: support for graph based databases. Currently Neo4j is supported.
  • spring-data-keyvalue: support for key-value databases. Currently Redis and Riak are supported and probably Membase will be supported in future.
  • spring-data-jdbc-ext: JDBC extensions, as example Oracle RAC connection failover is implemented.
  • spring-data-jpa: simplifies JPA based data access layer.

I would like to share with you how you can use Redis. First step is to  download it from redis.io web page. Here is useful site try.redis-db.com where we can run Redis commands and also read step by step tutorial. This tutorial shows us all structures Redis supports (list,set,sorted set and hashes) and some useful commands. A lot of reputable sites use Redis today .

After download and unpacking we should compile Redis (version 2.2 (it is release candidate) is preferable one to use since some commands do not work in version 2.0.4).

> make

> sudo make install

Once we run this commands we are all set to run the following five commands:

  • redis-benchmark – for benchmarking Redis server
  • redis-check-aof – check the AOF (Aggregate Objective Function), and it can repair that.
  • redis-check-dump – check rdb files for unprocessable opcodes.
  • redis-cli – Redis client.
  • redis-server – Redis server.

We can test Redis server.

>redis-server

[1055] 06 Jan 18:19:15 # Warning: no config file specified, using the default config. In order to specify a config file use ‘redis-server /path/to/redis.conf’

[1055] 06 Jan 18:19:15 * Server started, Redis version 2.0.4

[1055] 06 Jan 18:19:15 * The server is now ready to accept connections on port 6379

[1055] 06 Jan 18:19:15 – 0 clients connected (0 slaves), 1074272 bytes in use

and Redis client.

> redis-cli

redis> set my-super-key “my-super-value”

OK

Now we create a simple Java project in order to show how simple a spring-data-redis module essentially is.

> mvn archetype:create -DgroupId=info.pietrowski -DpackageName=info.pietrowski.redis -DartifactId=spring-data-redis -Dpackage=jar

Next we have to add in pom.xml milestone spring repository, and add spring-data-redis as dependence, after that all needed dependencies will be fetched.

Next we are creating resources folder under main folder, and create application.xml which will have all the configuration.

We can configure the JedisConnectionFactory,  in two different ways, One – we can provide JedisShardInfo object in shardInfo property or second – we can provide host (default localhost), port (default 6379), password (default empty) and timeout (default 2000) properties. One think to keep in mind is  that JedisShardInfo object has precedence and allows to setup weight, but only allows constructor injection.

We can set factory to use connection pooling by setting the value of propery  pooling to ‘true’ (default).

See application.xml comments to see three different way of configuration.

Note: There are two different libraries supported Jedis and JRedis, there have very similar names and both have the same factory name. See the difference (two r isn’t enough for me):

  • org.springframework.data.keyvalue.redis.connection.jedis.JedisConnectionFactory
  • org.springframework.data.keyvalue.redis.connection.jredis.JredisConnectionFactory

Similar to what we do in Spring, we configure template object providing it with connection factory. We will perform all the operations through this template object. By default we need to provide only Connection Factory, but there are more properties we can provide:

  • exposeConnection (default false) – if we return real connection or proxy object.
  • keySerializer, hashKeySerializer, valueSerializer, hashValueSerializer (default JdkSerializationRedisSerializer) which delegates serialization to default Java serialization mechanism.
  • stringSerializer (default StringRedisSerializer) which is simple String to byte[] (and back) serializer with UTF8 encoding.

We are ready to execute some code which will be cooperating with Redis instance. Spring-Data provide us with two ways of interaction, First is by using execute method and providing RedisCallback object. Second is by using *Operations helpers (it will be explained later)

When we are using RedisCallback we have access to low level Redis commands, see this list of interface (I won’t put all the method here because it is huge list):

Check RedisCallbackExample class, this was the hard way and the problem is we have to convert our objects into byte arrays in both directions, the second way is easier. Spring Data provides for us Operations objects, than we have much more simpler API and all byte<->object conversion is made by serializer we setup (or the default one). Higher level API (you will easily recognize *Operation *Commands equivalents):

Most of methods get key as first parameters so we have even better API for multiple operation on the same key:

Check RedisCallbackExample class to see some easy examples of *Operations usage. One important thing to mention is that you should use stringSerializers for keys, otherwise you will have problems from other clients, because standard serialization adds class information. Otherwise you end with such keys:

  1. “\xac\xed\x00\x05t\x00\x05atInt”
  2. “\xac\xed\x00\x05t\x00\nmySuperKey”
  3. “\xac\xed\x00\x05t\x00\bsuperKey”

Till now we just check API for Redis, but Spring Data offers more for us. All cool stuff is in org.springframework.data.keyvalue.redis.support package and all sub-packages. We have than:

  • RedisAtomicInteger – Atomic integer (CAS operation) backed by Redis.
  • RedisAtomicLong – Same as previous for Long.
  • RedisList – Redis extension for List, Queue, Deque, BlockingDeque and BlockingQueue with two additional methods List range(start, end) and RedisList trim(start, end).
  • RedisSet – Redis extension for Set with additional methods: diff, diffAndStore, intersect, intersectAndStore, union, unionAndStore.
  • RedisZSet – Redis extension for SortedSet. Note that Comparator is not applicable here so this interface extends normal Set and provide proper methods similar to SortedSet.
  • RedisMap – Redis extension for Map with additional Long increment(key, delta) method

Every interface currently have one Default implementation. Check application-support.xml for examples of configuration and RedisSupportClassesExample for examples of use. There is lot of useful information in the comments as well.

Summary

The library is first milestone release so there are minor bugs, documentation isn’t as perfect as we used to and current version needs no stable Redis server but this is definitely a great library which allow us to use all this cool NoSQL stuff in a “standard” Spring Data Access manner.

Awesome job!

This post is only useful if you checkout the code: from bitbucket , for the lazy ones here is spring-data-redis zip file as well.