Set up a maven web project in Intellij with Spring and JPA - Part Four

Hello, welcome the part four of this tutorial. Today we will be adding Spring configuration to our application.
Start by creating the following packages: blog.dao and blog.service.
The next thing we will be doing is adding the Spring configuration file: add applicationContext.xml file to your WEB-INF folder.

The basic setup of this file should look like this:

This configures the namespaces we will be needing in our configuration. Next we will have a look to what we will need specifically.



The first element we'll be adding is the dataSource bean, this bean will contain the location and configuration of our mysql database. root/root isn't very ideal but since it's just an example... :) you get the idea. 
    <bean class="org.springframework.jdbc.datasource.DriverManagerDataSource" id="dataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver">
        <property name="url" value="jdbc:mysql://localhost:3306/blog">
        <property name="username" value="root">
        <property name="password" value="root">
    </bean>

So we now configured a database, a driver to acces it, the location of our database and a username/password. This is all we will need for this tutorial, ofcourse further customization is possible.

Next bean to cover is a really cool feature of Spring: Component scanning. Component scanning will allow Spring to find your classes without having to explicitly declare them in xml, we will be using annotations instead (like we have seen @Entity in our domain). 
<context:component-scan base-package="blog.service blog.dao">

To make it even better this can be done in just one line of XML!

Now let's setup a transaction manager that will take care of the transaction management for us 
    <bean class="org.springframework.orm.jpa.JpaTransactionManager" name="transactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory">
     </bean>


    <tx:annotation-driven transaction-manager="transactionManager"/>

Note: using tx:annotation driven will let Spring autodetect @Transactional annotations in our code, more info on that later.

One last thing to do now, the hearth of JPA: the entity manager configuration!
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
          p:packagesToScan="blog.domain"
          p:dataSource-ref="dataSource"
          p:jpaVendorAdapter-ref="hibernateVendor"
          p:jpaPropertyMap-ref="jpaPropertyMap"
            />

    <util:map id="jpaPropertyMap">
        <entry key="hibernate.hbm2ddl.auto" value="update"/>
        <entry key="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/>
    </util:map>

    <bean id="hibernateVendor" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"
          p:showSql="true"
          p:generateDdl="true"/>

Quite some things to talk about here:

  • packagesToScan: scans for your entities in the blog.domain package
  • dataSource-ref links to your datasource
  • jpaVendorAdapter & jpaPropertyMap define properties to autogenerate tables and columns and what dialect to use, etc.
note: usage of p namespace.

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