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Expanded Audience – Frontegg – Security (partner)
announcement - icon User management is very complex, when implemented properly. No surprise here.

Not having to roll all of that out manually, but instead integrating a mature, fully-fledged solution - yeah, that makes a lot of sense.
That's basically what Frontegg is - User Management for your application. It's focused on making your app scalable, secure and enjoyable for your users.
From signup to authentication, it supports simple scenarios all the way to complex and custom application logic.

Have a look:

>> Elegant User Management, Tailor-made for B2B SaaS

NPI – Security Top – Temp – Non-Geo (Frontegg)

I just announced the new Learn Spring Security course, including the full material focused on the new OAuth2 stack in Spring Security 5:

>> CHECK OUT THE COURSE
NPI – Frontegg – Security – (partner)
announcement - icon User management is very complex, when implemented properly. No surprise here.

Not having to roll all of that out manually, but instead integrating a mature, fully-fledged solution - yeah, that makes a lot of sense.
That's basically what Frontegg is - User Management for your application. It's focused on making your app scalable, secure and enjoyable for your users.
From signup to authentication, it supports simple scenarios all the way to complex and custom application logic.

Have a look:

>> Elegant User Management, Tailor-made for B2B SaaS

NPI – Spring Top – Temp – Non-Geo (Lightrun)

Get started with Spring 5 and Spring Boot 2, through the reference Learn Spring course:

>> LEARN SPRING
NPI – Lightrun – Spring (partner)

We rely on other people’s code in our own work. Every day. It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production - debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky. It’s difficult to understand what talks to what and, specifically, which part of the underlying library is at fault.

Lightrun is a new kind of debugger.

It's one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics. No hotfixes, redeployments, or restarts required.

Learn more in this quick, 5-minute Lightrun tutorial:

>> The Essential List of Spring Boot Annotations and Their Use Cases

1. The Problem

This article will discuss one of the most common configuration problems in Spring – a namespace handler for one of the Spring namespaces is not found. Most of the time, this means one particular Spring jar is missing from the classpath – so let's go over what these missing schemas might be, and what the missing dependency is for each one.

Further reading:

XML-Based Injection in Spring

Learn how to perform an XML-based injection with Spring.

web.xml vs Initializer with Spring

A quick and practical guide to XML and Java config in Spring.

Top Spring Framework Interview Questions

A quick discussion of common questions about the Spring Framework that might come up during a job interview.

2. http://www.springframework.org/schema/security

The security namespace not being available is by far the most widely encountered problem in practice:

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/security" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:beans="http://www.springframework.org/schema/beans"
    xsi:schemaLocation="
        http://www.springframework.org/schema/security 
        http://www.springframework.org/schema/security/spring-security-3.2.xsd
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.1.xsd">

</beans:beans>

Which leads to the following exception:

org.springframework.beans.factory.parsing.BeanDefinitionParsingException: 
Configuration problem: 
Unable to locate Spring NamespaceHandler for XML schema namespace 
[http://www.springframework.org/schema/security]
Offending resource: class path resource [securityConfig.xml]

The solution is straightforward – the spring-security-config dependency is missing from the classpath of the project:

<dependency> 
   <groupId>org.springframework.security</groupId>
   <artifactId>spring-security-config</artifactId>
   <version>3.2.5.RELEASE</version>
</dependency>

This will put the correct namespace handler – in this case SecurityNamespaceHandler – on the classpath and ready to parse the elements in the security namespace.

The complete Maven configuration for a full Spring Security setup can be found in my previous Maven tutorial.

3. http://www.springframework.org/schema/aop

The same problem occurs when using the aop namespace without having the necessary aop spring library on the classpath:

<beans 
    xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop-4.1.xsd">

</beans>

The exact exception:

org.springframework.beans.factory.parsing.BeanDefinitionParsingException: 
Configuration problem: 
Unable to locate Spring NamespaceHandler for XML schema namespace 
[http://www.springframework.org/schema/aop]
Offending resource: ServletContext resource [/WEB-INF/webConfig.xml]

The solution is similar – the spring-aop jar needs to be added to the classpath of the project:

<dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-aop</artifactId>
   <version>4.1.0.RELEASE</version>
</dependency>

In this case, the AopNamespaceHandler will be present on the classpath after adding the new dependency.

4. http://www.springframework.org/schema/tx

Using the transaction namespace – a small but very useful namespace for the configuration of the transactional semantics:

<beans 
    xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx-4.1.xsd">

</beans>

will also result in an exception if the right jar is not on the classpath:

org.springframework.beans.factory.parsing.BeanDefinitionParsingException: 
Configuration problem: 
Unable to locate Spring NamespaceHandler for XML schema namespace
[http://www.springframework.org/schema/tx]
Offending resource: class path resource [daoConfig.xml]

The missing dependency here is spring-tx:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-tx</artifactId>
    <version>4.1.0.RELEASE</version>
</dependency>

Now, the right NamspaceHandler – namely TxNamespaceHandler – will be present on the classpath allowing the declarative transaction management with both XML and annotations.

5. http://www.springframework.org/schema/mvc

Moving forward to the mvc namespace:

<beans 
    xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:tx="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">

</beans>

The missing dependency will lead to the following exception:

org.springframework.beans.factory.parsing.BeanDefinitionParsingException: 
Configuration problem: 
Unable to locate Spring NamespaceHandler for XML schema namespace
[http://www.springframework.org/schema/mvc]
Offending resource: class path resource [webConfig.xml]

In this case, the missing dependency is spring-mvc:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>4.1.0.RELEASE</version>
</dependency>

Adding this to the pom.xml will add the MvcNamespaceHandler to the classpath – allowing the project to configure MVC semantics using the namespace.

6. Conclusion

Finally, if you're using Eclipse to manage the web server and deploy – make sure that the Deployment Assembly section of the project is correctly configured – namely that the Maven dependencies actually are included on the classpath at deployment time.

This tutorial discussed the usual suspects for the “Unable to locate Spring NamespaceHandler for XML schema namespace” problem and provided solutions for each occurrence.

Spring bottom

Get started with Spring 5 and Spring Boot 2, through the Learn Spring course:

>> THE COURSE
Security bottom

I just announced the new Learn Spring Security course, including the full material focused on the new OAuth2 stack in Spring Security 5:

>> CHECK OUT THE COURSE
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