On our new project we decided to develop backend as services deployed on Servicemix 4.2. To make it easier for developers more familiar with \u2018traditional\u2019 web applications based on spring+hibernate stack it should (at least partially) resemble such application. Therefore, we want to have following bundles:<\/p>\n
So far, so good. Additional requirements are:<\/p>\n
Now, the question is \u2013 how to achieve it in OSGI environment? There are some tutorials on the web, but I haven\u2019t found anything about this particular configuration, so I want to share our solution \u2013 as it wasn\u2019t as straightforward as one might expect.<\/p>\n
The very first problem was the structure of hibernate jars themselves. It turned out that simple<\/p>\n
is not enough when one wants to use annotations. The problem is that both hibernate-core, and hibernate-annotations are using same package, namely The solution is of course pretty simple \u2013 we have to create our own bundle, which embeds both hibernate jars. This can be achieved with following maven-bundle-plugin configuration:<\/p>\n Of course, you have to add hibernate dependencies to pom.<\/p>\n Servicemix has its own JTA TransactionManager, and at first I wanted to use it for managing our hibernate transactions. Unfortunatelly it turned to be somewhat tricky, so I decided to use simple solution, i.e. Then, in service bundle we import it, and configure declarative transactions:<\/p>\n So far, it doesn\u2019t look much more complicated than in traditional, monolithic war application. But there is one more caveat:<\/p>\n At first I thought it\u2019s a matter of some misconfigured import\/export declarations in some of our bundles. However, after some googling it turned out that it\u2019s Hibernate\u2019s bug<\/a><\/p>\n It is caused by using Thread context classloader when obtaining connection. It looks that the bug itself is already fixed, but we didn\u2019t want to change to Hibernate 3.5 just because of that.<\/p>\n It turns out that there is quire simple workaround \u2013 you just need to make Spring aspect that will set context classloader to proper one (i.e. bundle class loader) before opening hibernate session, and you\u2019re done. But again, using Servicemix makes it slightly harded, as it turns out that using @AspectJ style poses some difficulties (see e.g. this thread<\/a>).<\/p>\n But it turns out that there is pretty simple solution \u2013 use old, Spring 1.x-style aspects :). This requires a bit more boilerplate xml, but at least we got it working pretty quickly.<\/p>\n The aspect class, setting proper classloader:<\/p>\n The xml config:<\/p>\n Final remark \u2013 now the service bundle has to import org.hibernate.jdbc<\/strong> to make it all work \u2013 as its classloader is used to initialize connection now.<\/p>\n To sum up: this is definitely not the most elegant solution one can imagine- but it\u2019s working.<\/p>\n","protected":false},"excerpt":{"rendered":"On our new project we decided to develop backend as services deployed on Servicemix 4.2. To make it…\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[43,44,42],"class_list":{"0":"post-201","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-development-design","7":"tag-hibernate","8":"tag-osgi","9":"tag-spring-framework"},"_links":{"self":[{"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/posts\/201","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/comments?post=201"}],"version-history":[{"count":17,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/posts\/201\/revisions"}],"predecessor-version":[{"id":15345,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/posts\/201\/revisions\/15345"}],"wp:attachment":[{"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/media?parent=201"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/categories?post=201"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/touk.pl\/blog\/wp-json\/wp\/v2\/tags?post=201"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}wrap:mvn:org.hibernate:hibernate:3.3.1.GA<\/code><\/p>\norg.hibernate.cfg<\/code>. This is pretty anti-OSGI design, as OSGI bundle can use package exported by exactly one bundle.<\/p>\n \r\n\r\n *;uses:=\"org.hibernate\";version=3.3.1.GA\r\n !*\r\n *;scope=compile|runtime;type=!pom;inline=true<\/pre>\n
Session factory and transaction management<\/h3>\n
org.springframework.orm.hibernate.HibernateTransactionManager<\/code>. It is declared in our dao bundle and exported as OSGI service:<\/p>\n\t\r\n\r\n org.springframework.transaction.PlatformTransactionManager<\/pre>\n
<\/pre>\n
org.hibernate.jdbc.ConnectionWrapper is not visible from class loader<\/h3>\n
public class AspectFix implements MethodInterceptor {\r\n\r\n public Object invoke(MethodInvocation invocation) throws Throwable {\r\n ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();\r\n Thread.currentThread().setContextClassLoader(getClass().getClassLoader());\r\n try {\r\n return invocation.proceed();\r\n }\r\n finally{ Thread.currentThread().setContextClassLoader(contextClassLoader);\r\n }\r\n }<\/pre>\n\r\n\r\n .*\r\n\r\n *Service\r\n\r\n fix<\/pre>\n