Spring Data JPA Query Methods

 Spring Data JPA Queries are a great way to create queries derived from the method name without needing to write tons of boiler-plate code to create connection & query, execute it and then process the result set. This generally works fine for simple queries and method names are very explicit in pointing out what is being returned by that method so the code is more readable and maintainable. To make this work successfully, the method name has to follow certain conventions:

1. Method names usually start with the word "find"
2. Filter clauses are added to the function name as "findBy<ColumnName>" which creates queries of the form "where <ColumnName> = ?"
3. Multiple Filter clauses are supported using And / Or clauses 
1. And can be used as "findBy<Col1>And<Col2>"  which creates the query "where <Col1> = ? and <Col2> = ?"
2. Or can be used as "findBy<Col1>Or<Col2>"  which creates the query "where <Col1> = ? or <Col2> = ?"
4. Similarly other operators are supported on the lines of Between, After, Before, LessThan, GreaterThan, Like, etc
5. Ordering of the results can be delegated to the database by adding "OrderBy" to the function name as "findBy<Col1>OrderBy<Col2><Asc|Desc><Col3><Asc|Desc>"

Here is a handy table of supported keywords inside method names taken from the Spring Data documentation:

Keyword	Sample	JPQL snippet
Distinct	findDistinctByLastnameAndFirstname	select distinct …​ where x.lastname = ?1 and x.firstname = ?2
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is, Equals	findByFirstname,findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age <= ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull, Null	findByAge(Is)Null	… where x.age is null
IsNotNull, NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1 (parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1 (parameter bound with prepended %)
Containing	findByFirstnameContaining	… where x.firstname like ?1 (parameter bound wrapped in %)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection<Age> ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection<Age> ages)	… where x.age not in ?1
True	findByActiveTrue()	… where x.active = true
False	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstname) = UPPER(?1)

Solve Spring NoUniqueBeanDefinitionException

I encountered the NoUniqueBeanDefinitionException where-in Spring was unable to which class to inject for an Autowired variable even though the it was properly qualified!

This happened because the Qualifier did not get post-processed and so multiple implementations of the Interface type of the variable being injected were now available in the classpath. So Spring found more that one instance and was unable to decide which instance to inject for the particular Autowired target.

The turn on the default AutowiredAnnotationBeanPostProcessor which processes the @Qualifier , you need to add the line to the beans section of your spring configuration. Since this was missing from the beans section of the configuration file, the Qualifier annotation was ignored in this code:

    @Autowired
    public void setDao(@Qualifier("myDaoImpl") MyDAO dao) {

And here is a snippet of the exception that was logged:

 java.lang.RuntimeException: org.springframework.beans.factory.BeanCreationException: Injection of autowired dependencies failed for class [class my.package.impl.name.MyBeanClassName]; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire method: public void my.package.impl.name.MyBeanClassName.setDao(my.package.intf.name.MyDAO); nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [my.package.intf.name.MyDAO] is defined: expected single matching bean but found 4: myDaoImpl,secondDaoImpl,thirdDaoImpl,fourthDaoImpl

This error was resolved after adding the below line to the beans section of spring configuration:

<context:annotation-config></context:annotation-config>

Upgrade from Spring 2.5.x to Spring 4.1.x - JBoss

After completing the steps mentioned in my previous post for Upgrading Spring 2.5.x to Spring 4.1.x, the project compiles without problems, however, JBoss deployment does not work as it does not get all the required new Spring Jars.

The Spring component jars also need to be added to the JBoss classpath. However, here are a few specific exceptions that point to requiring specific jars in the JBoss classpath as below.

To resolve the below error, add spring-context.jar to JBoss library path:
java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy
at sun.reflect.annotation.AnnotationParser.parseClassArray(AnnotationParser.java:653)
at sun.reflect.annotation.AnnotationParser.parseArray(AnnotationParser.java:460)
at sun.reflect.annotation.AnnotationParser.parseMemberValue(AnnotationParser.java:286)
at sun.reflect.annotation.AnnotationParser.parseAnnotation(AnnotationParser.java:222)
at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:69)
at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:52)
at java.lang.Class.initAnnotationsIfNecessary(Class.java:3079)


To resolve the below error, add spring-beans.jar to JBoss library path
java.lang.NoClassDefFoundError: org/springframework/beans/factory/BeanFactory
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2436)
at java.lang.Class.getDeclaredMethods(Class.java:1793)
at org.jboss.ejb3.interceptor.InterceptorInfoRepository$AnnotationInitialiser.getInfo(InterceptorInfoRepository.java:704)
at org.jboss.ejb3.interceptor.InterceptorInfoRepository.initialiseFromAnnotations(InterceptorInfoRepository.java:469)
at org.jboss.ejb3.interceptor.InterceptorInfoRepository.getOrInitialiseFromAnnotations(InterceptorInfoRepository.java:451)
at org.jboss.ejb3.interceptor.InterceptorInfoRepository.getInterceptorsFromAnnotation(InterceptorInfoRepository.java:341)
at org.jboss.ejb3.interceptor.InterceptorInfoRepository.getClassInterceptors(InterceptorInfoRepository.java:139)
at org.jboss.ejb3.EJBContainer.initialiseInterceptors(EJBContainer.java:737)
at org.jboss.ejb3.EJBContainer.getClassInterceptors(EJBContainer.java:429)

Hopefully this should resolve all issues for a successful upgrade of Spring 2.5.x to Spring 4.1.x!

Upgrade from Spring 2.5.x to Spring 4.1.x

I am upgrading Spring libraries of a critical project from Spring 2.5.x to the latest available release which is Spring 4.1.6 right now. One of the major issues I faced is that the packaging strategy was changed in Spring 3.0 release. Earlier, a single spring.jar with all jars and required libraries was provided, but this was discontinued from the 3.0 release. Now we would need to include each jar individually as per requirements - one jar for all situations doesn't exist anymore.

So, now you need to download individual spring component jars from the Maven Repository. The jars required are:

1. spring-aop.jar
2. spring-beans.jar
3. spring-context.jar
4. spring-core.jar
5. spring-expression.jar
6. aopalliance-1.0.jar - third-party jar

The third-party jar aopalliance-1.0 is required only if you use org.springframework.aop and it can be downloaded from here. This was earlier on bundled in the spring.jar and so now has to be added separately as required.

You can download the corresponding javadoc and source files by going to the Maven website and searching for:

• g:"org.springframework" AND v:"4.1.6.RELEASE" - for Spring components
  
• g:"aopalliance" - for aopalliance

Now that all the required jars are downloaded, spring-core jar will need to be included in most projects; here is a simple guide to when to include rest of the jars.

Add spring-beans.jar to classpath when you see the below or similar error during compilation:
Caused by: java.lang.ClassNotFoundException: org.springframework.beans.factory.NoSuchBeanDefinitionException
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Add spring-context.jar to classpath when you see the below or similar error during compilation:
Caused by: java.lang.ClassNotFoundException: org.springframework.context.access.ContextSingletonBeanFactoryLocator
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Add spring-expression.jar to classpath when you see the below or similar error during compilation:
Caused by: java.lang.ClassNotFoundException: org.springframework.expression.ParserContext
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Add spring-aop.jar to classpath when you see the below or similar error during compilation:
The type org.springframework.aop.TargetSource cannot be resolved. It is indirectly referenced from required .class files
OR

Caused by: java.lang.ClassNotFoundException: org.springframework.aop.framework.ProxyFactoryBean

Add aopalliance-1.0.jar to classpath when you see the below or similar error during compilation:
The type org.aopalliance.aop.Advice cannot be resolved. It is indirectly referenced from required .class files
OR

Caused by: java.lang.ClassNotFoundException: org.aopalliance.intercept.MethodInterceptor

That's it - you should be all set and upgraded to the latest version of Spring after this exercise - no code change required!