paulc4 / mvc-exceptions

Demo of points covered on my MVC Exceptions blog

mvc-exceptions

Project Overview

• Last updated July 2024
• This project is built using release 2.7.18 of Spring Boot, Java 8 and Spring 5.3.31 - see pom.xml.
• Web pages use Thymeleaf 3.0.15 and Bootstrap 4.5.3.
• The POM builds a JAR file, not a WAR, so you must run it as a Java application. Use mvn exec:java or mvn spring-boot:run to run it, then goto http://localhost:8080.
• If you wish to build a WAR, see pom-war.xml

This application demos most of the points covered on my MVC Exceptions blog:

• Local copy is here: blog.md.
• Original blog: https://spring.io/blog/2013/11/01/exception-handling-in-spring-mvc.

Release History

• November 2013: V1
• October 2014: V2
• April 2018: V2.0.1
• January 2021: V2.1.0
• January 2021: V2.1.1

Application Overview

The most significant files are:

Demo 1

Controller with @ExceptionHandler methods

• src/main/java/demo1/web/ExceptionHandlingController.java
  • A controller that raises exceptions and provides its own handlers to catch and process them.

Demo 2

Controller relying on a ControllerAdvice to handle its exceptions.

• src/main/java/demo2/web/ControllerWithoutExceptionHandlers.java

  • A controller with all the same handlers as ExceptionHandlingController (so they all throw exceptions) but no handler methods.

• src/main/java/demo2/web/GlobalControllerExceptionHandler.java

  • @ControllerAdvice class with all the same handlers as ExceptionHandlingController, but they would apply to all controllers.

Demo 3 and 4

Exception handling using a SimpleMappingExceptionResolver. When running in demo mode (profile is set to demo-config, which is setup by default), it defines a SimpleMappingExceptionResolver subclass that can be enabled (Demo 3) or disabled (Demo 4) to show the difference.

• src/main/java/demo3/config/DemoExceptionConfiguration.java
  • Java configuration to setup the beans for this demo.
• src/main/java/demo3/web/ExceptionThrowingController.java
  • Controller used by the demo.
• src/main/java/demo3/web/SwitchableSimpleMappingExceptionResolver.java
  • The resolver subclass described above.
• src/main/java/demo3/web/ExceptionThrowingController.java
  • Controller that provides /simpleMappingExceptionResolver/on and /simpleMappingExceptionResolver/off for switching the resolver on/off.

Demo 5

• ReturnOrRedirectController
  • Controller highlighting how Spring Boot implements its error-page mechanism.

Exceptions

• src/main/java/demo/exceptions/CustomException.java
• src/main/java/demo/exceptions/DatabaseException.java
• src/main/java/demo/exceptions/InvalidCreditCardException.java
• src/main/java/demo/exceptions/OrderNotFoundException.java
• src/main/java/demo/exceptions/UnhandledException.java
  • Custom exceptions - see blog for usage.
• src/main/java/org/springframework/dao/DataAccessException.java
  • Example of a predefined annotation, copied from Spring.
• src/main/java/org/springframework/dao/DataIntegrityViolationException.java
  • Example of a predefined annotation, copied from Spring.

Application Setup

The Demo configuration profile is useful for this demo application, but not typical. So two other profiles are provided to configure a SimpleMappingExceptionResolver in a more typical way using either Java configuration or an XML bean file.

• src/main/java/demo/main/Main.java
  • Main entry point for the application. Can run as a Java application (using an embedded Tomcat container) or as a WAR inside a container. Sets a few initialization properties and Spring Bean profile to use. Available profiles are demo-config (default), java-config, xml-config.
• src/main/java/demo/main/Profiles.java
  • The Spring Bean profiles used in the application.
• src/main/java/demo/config/ExceptionConfiguration.java
  • Java configuration class to setup a SimpleMappingExceptionResolver. Only used if the java-config profile is active.
• src/main/resources/mvc-configuration.xml
  • XML alternative to ExceptionConfiguration. Also sets up a SimpleMappingExceptionResolver. Only used if the xml-config profile is active.
• src/main/java/demo/config/ResponseDataControllerAdvice
  • Controller advice that puts useful data into the model for every request.

Utility Classes

• src/main/java/demo/utils/BeanLogger.java
  • Simple BeanPostProcessor to log all beans created. Not required by the demo, but as Spring Boot does so much, it allows all the beans created to be easily logged. And a lot less output than enabling debug=true.

Templates

All the views used, generated via Thymeleaf.

• Error views

  • src/main/resources/templates/creditCardError.html
  • src/main/resources/templates/databaseError.html
  • src/main/resources/templates/databaseException.html
  • src/main/resources/templates/error.html
  • src/main/resources/templates/exceptionPage.html
  • src/main/resources/templates/support.html

• Web Pages

  • src/main/resources/templates/index.html - Home page
  • src/main/resources/templates/local.html - Demo 1
  • src/main/resources/templates/global.html - Demo 2
  • src/main/resources/templates/unannotated.html - Demo 3
  • src/main/resources/templates/nohandler.html - Demo 4
  • src/main/resources/templates/demo5.html - Demo 5

Build

• pom.xml

  • Maven POM - notice how short it is - Spring Boot does most of the work. However heed the comments in the file.
  • Build in the usual way: mvn package to create an executable JAR with embedded Tomcat.
  • You can also run the demo using java -jar target/mvc-exceptions-2.0.1-RELEASE.jar

• pom-war.xml - If you prefer to build a traditional WAR file instead of an executable JAR.

  • Build using mvn -f pom-war.xml package

Examples

Not used by the application, but provided as sample code.

• src/main/java/demo/example/ExampleExceptionHandlerExceptionResolver.java
  • Unused in the demo (to keep it simple), but implements the example discussed in the blog.
• src/main/java/demo/example/ExampleSimpleMappingExceptionResolver.java
  • Unused in the demo (to keep it simple), but implements the example shown in the blog (called MySimpleMappingExceptionResolver in the blog article).