Spring with Spark Framework for Microservices

Recently, my team decided to use Spark to build our new REST api.  Spark seems easy with less coding.  We still wanted to use Spring for dependency injection.  We also wanted to use Tomcat as the standalone web container.  After some research, we figured out how to build the REST api with Spring, Spark and Tomcat.

1. Create class SpringSparkFilter which extends SparkFilter. Override method getApplication:
2. Create class MySparkApplication, which implements SparkApplication. Implement init method:
3. Configure web.xml to use SpringSparkFilter:

Then either build a war file, and deploy it to tomcat or use tomcat7-maven-plugin for test run.  I usually use tomcat7-maven-plugin for fast development.  Here is the command:

mvn tomcat7:run

Then access http://localhost:8080/current-date.  The complete example can be found here.

Using embedded mysql database for unit test with maven and spring

I used H2 in memory database to unit test my DAO.  However, my production database is MySQL.
Generally, H2 is compatible with MySQL.  However, H2 doesn't support ENUM type yet, and my schema uses ENUM for a column definition.  Inspired by this post and another, I successfully used embedded MySQL for unit test.  Here is what I did:

1.  Add mysql-connector-mxj dependency:


2. Create EmbeddedMysqlDatabase.java and EmbeddedMysqlDatabaseBuilder.java

3. Create spring bean datasource:
4. Run unit test with Spring:
A couple things are worth mentioning:

1. The test uses Spring annotation @DirtiesContext(classMode = ClassMode.AFTER_EACH_TEST_METHOD) which reload the context after every test method.  It means every test method starts a new mysql instance.  You may group test methods to 2 different categories, one changes data, and another not.  For those methods don't change data, only need to create one instance of mysql to speed up testing.

2. If you see the following error message on Linux server:
/lib64/libc.so.6: version `GLIBC_2.7' not found (required by /tmp/test_db_2420035739165052/bin/mysqld)

You need to either downgrade mysql-connector-mxj to 5.0.11 or upgrade your linux OS.  I got the above error message on CentOS 5.4 with 5.0.12, but no problem with 5.0.11. However, 5.0.11 isn't in any public maven repo, but you can download it from here and install it to your local repo, or upload to your company's repo. Using the following command to check CentOS version:

cat /etc/redhat-release

3. The code is tested on Mac and CentOS only, and can be downloaded from github

Example for enabling CORS support in Spring Rest Api 3.2

My last year's post "Enable CORS support in REST services with Spring 3.1" seems causing some confusion.  I decided to create an example to show how to enable CORS with Spring rest api.  The CorsFilter is same as before:


Below are 2 endpoints from EmployeeController.java:

The update method adds the header Access-Control-Allow-Origin with "*", but delete method doesn't.  Therefore, the update method is enabled with CORS, but delete isn't.  If delete endpoint is called, the following error will be shown in Chrome:

"cannot load http://localhost:8080/rest/employee/1. Origin http://127.0.0.1:8080 is not allowed by Access-Control-Allow-Origin."

However, the delete method is still invoked on the server side since the pre-flight request (OPTIONS)
allows DELETE method to be called.

The entire project can be downloaded from github.  Following README to test it.

My intention was to disable/enable CORS support in each individual method by setting "Access-Control-Allow-Origin", but it seems not working as expected:  Although the browser returns correct info, the method call is still invoked on the server side even Access-Control-Allow-Origin is not set.  If you are allowed to enable all endpoints with CORS support, the code can be simplified as below:

The only difference is that addHeader("Access-Control-Allow-Origin") is moved out the if check. And then the update method can be simplified as:

The code can be downloaded from github too.

Enable Spring Jdbc Transaction with Annotation

Spring 3.1 introduced a new annotation @EnableTransactionManagement.  With it, all xml configuration can be got rid of now.  Here is the example on how to use it:

@Configuration
@EnableTransactionManagement
public class JdbcConfig {

    @Bean
    public DataSource dataSource() {
    //config datasource      
    }

    @Bean
    public PlatformTransactionManager txManager() {
        return new DataSourceTransactionManager(dataSource());
    }

    @Bean
    public MyDao myDao() {
        MyDaoJdbc dao = new MyDaoJdbc();
        dao.setDataSource(dataSource());
        return dao;
    }
}

Next you need to annote your dao with @Transactional.  The source code can be found at github:

https://github.com/zhentao/spring-jdbc-transaction-example