Spring FAQs-->3

Spring interview questions and answers

41. What is Spring's JdbcTemplate ?

Spring's JdbcTemplate is central class to interact with a database through JDBC. JdbcTemplate provides many convenience methods for doing things such as converting database data into primitives or objects, executing prepared and callable statements, and providing custom database error handling.
JdbcTemplate template = new JdbcTemplate(myDataSource);

42. What is PreparedStatementCreator ?

PreparedStatementCreator:

• Is one of the most common used interfaces for writing data to database.
• Has one method – createPreparedStatement(Connection)
• Responsible for creating a PreparedStatement.
• Does not need to handle SQLExceptions.

43. What is SQLProvider ?

SQLProvider:

• Has one method – getSql()
• Typically implemented by PreparedStatementCreator implementers.
• Useful for debugging.

44. What is RowCallbackHandler ?

The RowCallbackHandler interface extracts values from each row of a ResultSet.

• Has one method – processRow(ResultSet)
• Called for each row in ResultSet.
• Typically stateful.

45. What are the differences between EJB and Spring ?

Spring and EJB feature comparison.

Feature		EJB	Spring
Transaction management		Must use a JTA transaction manager. Supports transactions that span remote method calls.	Supports multiple transaction environments through its PlatformTransactionManager interface, including JTA, Hibernate, JDO, and JDBC. Does not natively support distributed transactions—it must be used with a JTA transaction manager.
Declarative transaction support		Can define transactions declaratively through the deployment descriptor. Can define transaction behavior per method or per class by using the wildcard character *. Cannot declaratively define rollback behavior—this must be done programmatically.	Can define transactions declaratively through the Spring configuration file or through class metadata. Can define which methods to apply transaction behavior explicitly or by using regular expressions. Can declaratively define rollback behavior per method and per exception type.
Persistence		Supports programmatic bean-managed persistence and declarative container managed persistence.	Provides a framework for integrating with several persistence technologies, including JDBC, Hibernate, JDO, and iBATIS.
Declarative security		Supports declarative security through users and roles. The management and implementation of users and roles is container specific. Declarative security is configured in the deployment descriptor.	No security implementation out-of-the box. Acegi, an open source security framework built on top of Spring, provides declarative security through the Spring configuration file or class metadata.
Distributed computing		Provides container-managed remote method calls.	Provides proxying for remote calls via RMI, JAX-RPC, and web services.

46 . Do I need any other SOAP framework to run Spring Web Services?

You don't need any other SOAP framework to use Spring Web services, though it can use

some of the features of Axis 1 and 2.

47 . I get NAMESPACE_ERR exceptions when using Spring-WS. What can I do about it?

If you get the following Exception:
NAMESPACE_ERR: An attempt is made to create or change an object in a way which is incorrect with regard to namespaces.
              
Most often, this exception is related to an older version of Xalan being used. Make sure to upgrade to 2.7.0.

48 .Does Spring-WS run under Java 1.3?

Spring Web Services requires Java 1.4 or higher.

49. Does Spring-WS work under Java 1.4?

Spring Web Services works under Java 1.4, but it requires some effort to make it work. Java 1.4 is bundled with the older XML parser Crimson, which does not handle namespaces correctly. Additionally, it is bundled with an older version of Xalan, which also has problems. Unfortunately, placing newer versions of these on the class path does not override them. .
The only solution that works is to add newer versions of Xerces and Xalan in the lib/endorsed directory of your JDK, as explained in those FAQs (i.e.$JAVA_HOME/lib/endorsed). The following libraries are known to work with Java 1.4.2:

Library	Version
Xerces	2.8.1
Xalan	2.7.0
XML-APIs	1.3.04
SAAJ	1.2

If you want to use WS-Security, note that the XwsSecurityInterceptor requires Java 5, because an underlying library (XWSS) requires it. Instead, you can use the Wss4jSecurityInterceptor.

50 .Does Spring-WS work under Java 1.6?

Java 1.6 ships with SAAJ 1.3, JAXB 2.0, and JAXP 1.4 (a custom version of Xerces and Xalan). Overriding these libraries by putting different version on the classpath will result in various classloading issues, or exceptions in org.apache.xml.serializer.ToXMLSAXHandler. The only option for using more recent versions is to put the newer version in the endorsed directory (see above).

51 . Why do the Spring-WS unit tests fail under Mac OS X?

For some reason, Apple decided to include a Java 1.4 compatibility jar with their JDK 1.5. This jar includes the XML parsers which were included in Java 1.4. No other JDK distribution does this, so it is unclear what the purpose of this compatibility jar is.
The jar can be found at /System/Library/Frameworks/JavaVM.framework/Versions/1.5.0/Classes/.compatibility/14compatibility.jar. You can safely remove or rename it, and the tests will run again.

52 . What is SAAJ?

SAAJ is the SOAP with Attachments API for Java. Like most Java EE libraries, it consists of a set of interfaces (saaj-api.jar), and implementations (saaj-impl.jar). When running in a Application Server, the implementation is typically provided by the application server. Previously, SAAJ has been part of JAXM, but it has been released as a seperate API as part of the , and also as part of J2EE 1.4. SAAJ is generally known as the packagejavax.xml.soap.
Spring-WS uses this standard SAAJ library to create representations of SOAP messages. Alternatively, it can use

53 . What version of SAAJ does my application server support?

Application Server		SAAJ Version
BEA WebLogic 8		1.1
BEA WebLogic 9		1.1/1.2*
BEA WebLogic 10		1.3**
IBM WebSphere 6		1.2
SUN Glassfish 1		1.3
JBoss 4.2		1.3***

54 .I get a NoSuchMethodError when using SAAJ. What can I do about it?

If you get the following stack trace:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.ws.soap.saaj.SaajSoapMessageFactory' defined in ServletContext resource [/WEB-INF/springws-servlet.xml]:
Invocation of init method failed;
nested exception is java.lang.NoSuchMethodError:
javax.xml.soap.MessageFactory.newInstance(Ljava/lang/String;)Ljavax/xml/soap/MessageFactory;
Caused by:
java.lang.NoSuchMethodError:
javax.xml.soap.MessageFactory.newInstance(Ljava/lang/String;)Ljavax/xml/soap/MessageFactory;
              
Like most J2EE libraries, SAAJ consists of two parts: the API that consists of interfaces (saaj-api.jar) and the implementation (saaj-impl.jar). The stack trace is due to the fact that you are using a new version of the API (SAAJ 1.3), while your application server provides an earlier version of the implementation (SAAJ 1.2 or even 1.1). Spring-WS supports all three versions of SAAJ (1.1 through 1.3), but things break when it sees the 1.3 API, while there is no 1.3 implementation.
The solution therefore is quite simple: to remove the newer 1.3 version of the API, from the class path, and replace it with the version supported by your application server.

55 . I get an UnsupportedOperationException "This class does not support SAAJ 1.1" when I use SAAJ under WebLogic 9. What can I do about it?

WebLogic 9 has a known bug in the SAAJ 1.2 implementation: it implement all the 1.2 interfaces, but throws UnsupportedOperationExceptions when you call them. Confusingly, the exception message is This class does not support SAAJ 1.1, even though it supports SAAJ 1.1 just fine; it just doesn't support SAAJ 1.2. See alsot Spring-WS has a workaround for this, we basically use SAAJ 1.1 only when dealing with WebLogic 9. Unfortunately, other frameworks which depend on SAAJ, such as XWSS, do not have this workaround. These frameworks happily call SAAJ 1.2 methods, which throw this exception.
The solution is to not use BEA's version of SAAJ, but to use another implementation, like the one from Axis 1, or SUN. In you application context, use the following:
<bean id="messageFactory" class="org.springframework.ws.soap.saaj.SaajSoapMessageFactory">
    <property name="messageFactory">
        <bean class="com.sun.xml.messaging.saaj.soap.MessageFactoryImpl"/>
    </property>
</bean>
                  

56 . I get an UnsupportedOperationException "This class does not support SAAJ 1.1" when I use SAAJ under WebLogic 10. What can I do about it?

Weblogic 10 ships with two SAAJ implementations. By default the buggy 9.x implementation is used (which lives in the package weblogic.webservice.core.soap), but there is a new implementation, which supports SAAJ 1.3 (which lives in the package weblogic.xml.saaj). By looking at the DEBUG logging when Spring Web Services starts up, you can see which SAAJ implementation is used.
To use this new version, you have to create a message factory bean like so:
<bean id="messageFactory" class="org.springframework.ws.soap.saaj.SaajSoapMessageFactory">
    <property name="messageFactory">
        <bean class="weblogic.xml.saaj.MessageFactoryImpl"/>
    </property>
</bean>
                   

57 . I get an IndexOutOfBoundsException when I use SAAJ under JBoss. What can I do about it?

The SAAJ implementation provided by JBoss has some issues. The solution is therefore not to use the JBoss implementation, but to use another implementation. For instance, you can use SUN's reference implementation like so:
<bean id="messageFactory" class="org.springframework.ws.soap.saaj.SaajSoapMessageFactory">
    <property name="messageFactory">
        <bean class="com.sun.xml.messaging.saaj.soap.ver1_1.SOAPMessageFactory1_1Impl"/>
    </property>
</bean>
                  

58 . Does Spring-WS run on IBM WebSphere?

WebSphere bundles some libraries which are out-of-date, and need to be upgraded with more recent versions. Specifically, this includes XML-apis, Xerces, Xalan, and WSDL4J.
There are a couple of ways to upgrade these libraries, all using parent-last or application-first classloading.

• Package the libraries as part of the WAR (in WEB-INF/lib), and run the web application with the parent-last (application-first) classloading.
• Package the libraries as part of the EAR, add class-path entries to the manifest of the web application, and run the entire application with the parent-last classloading.
• Create a new classloader in the WebSphere console, and associate the libraries with. Set this classloader to parent-last.

The last approach has the advantage of restricting the parent-last classloading to the conflicting libraries only, and not to the entire application.

59. Why does Spring-WS only support contract-first? 

Note that Spring-WS only requires you to write the XSD; the WSDL can be generated from that.

60 . How do I retrieve the WSDL from a Service?

The &WSDL query parameter does not work.
The &WSDL query parameter is a way to get a WSDL of a class. In SWS, a service is generally not implemented as a single class, but as a collection of endpoints.
There are two ways to expose a WSDL:

• Simply add the WSDL to the root of the WAR, and the file is served normally. This has the disadvantage that the "location" attribute in the WSDL is static, i.e. it does not necessarily reflect the host name of the server. You can transform locations by using a WsdlDefinitionHandlerAdapter.
• Use theMessageDispatcherServlet, which is done is the samples. Every WsdlDefinition listed in the *-servlet.xml will be exposed under the bean name. So if you define a WsdlDefinition namedecho, it will be exposed as echo.wsdl (i.e.http://localhost:8080/echo/echo.wsdl).