Introduction

This is example code that randomly compares Guice error handling with Spring error handling. It uses the example shown here.

Guice's error handling is one of the framework's great strengths.

• Lots of mistakes get detected at compile time.
• You will see all the mistakes you made in one go, not only the first one.
• Guice links to the offending configuration code in the error message, on which you can click to navigate to the line of configuration that matters (Java IDE feature).
• Guice's error messages actually help.

THIS IS NOT A COMPLETE COMPARISON, AND WILL NEVER BE. I will add to this document over time.

One

Typo in Guice's @Named or Spring's corresponding @Qualifier configuration.

Guice:

bindConstant().annotatedWith(Names.named("colory")).to("White");

Guice Result:

Exception in thread "main" com.google.inject.CreationException: Guice configuration errors:

1) Error at demo.Cap.<init>(Cap.java:10):
 Binding to java.lang.String annotated with @com.google.inject.name.Named(value=color) not found. Annotations on other bindings to that type include: [@com.google.inject.name.Named(value=colory)]

1 error[s]
	at com.google.inject.BinderImpl.createInjector(BinderImpl.java:277)
	at com.google.inject.Guice.createInjector(Guice.java:79)
	at com.google.inject.Guice.createInjector(Guice.java:53)
	at com.google.inject.Guice.createInjector(Guice.java:43)
	at demo.error.Error1.main(Error1.java:14)

As you can see, Guice's message is helpful, and shows you the annotation that would have been right.

Spring:

<bean class="java.lang.String" factory-method="valueOf">
    <constructor-arg value="White"/>
    <!-- Typo in value -->
    <qualifier value="colory"/>
</bean>

Spring Result (I added some line breaks):

Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'demo.spring.xml.Cap#0' defined in class path resource [demo/spring/xml/error/error1.xml]:
Unsatisfied dependency expressed through constructor argument with index 0 of type [java.lang.String]: 
No unique bean of type [java.lang.String] is defined: Unsatisfied dependency of type [class java.lang.String]: expected at least 1 matching bean
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:570)
	at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:190)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:893)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:803)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:437)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:404)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:375)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:263)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:170)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:260)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:184)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:163)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:430)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at demo.spring.xml.error.Error1.main(Error1.java:11)

Expected at least 1 matching bean? So did I, man.

Two

Binding to a regular class where an annotation is required.

Guice:

bind(Cap.class).annotatedWith(Cap.class).to(Cap.class);

Guice Result:

Compile error.

Guice will not compile this code; the Java compiler will make sure that you pass in an annotation class.

Spring:

<bean class="demo.spring.xml.Cap">
    <qualifier type="demo.spring.xml.Cap"/>
</bean>

Spring Result (Added line breaks):

org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'demo.spring.xml.Smurf#0' defined in class path resource [demo/spring/xml/error/error2.xml]:
Unsatisfied dependency expressed through constructor argument with index 0 of type [demo.spring.xml.Cap]:
No unique bean of type [demo.spring.xml.Cap] is defined: Unsatisfied dependency of type [class demo.spring.xml.Cap]: expected at least 1 matching bean
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:570)
	at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:190)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:893)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:803)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:437)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:404)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:375)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:263)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:170)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:260)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:184)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:163)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:430)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at demo.spring.xml.error.Error2.main(Error2.java:11)

Rrriiight.

Three

Converting an enum String to an enum value.

public enum Number {
    ONE, TWO
}

// Added for use with Spring
public class NumberUser {
    public NumberUser(demo.error.Number n) {
        System.out.println(n);
    }
}

Guice:

// Enum with typo
bindConstant().annotatedWith(Names.named("two")).to("TW");

Guice Result (Added line breaks):

Exception in thread "main" com.google.inject.ConfigurationException:
Error at [unknown source] Error converting String constant bound at demo.error.Error3$1.configure(Error3.java:15) to demo.error.Number:
No enum const class demo.error.Number.TW
	at com.google.inject.BinderImpl$RuntimeErrorHandler.handle(BinderImpl.java:426)
	at com.google.inject.AbstractErrorHandler.handle(AbstractErrorHandler.java:30)
	at com.google.inject.InjectorImpl.handleConstantConversionError(InjectorImpl.java:315)
	at com.google.inject.InjectorImpl.getInternalFactory(InjectorImpl.java:245)
	at com.google.inject.InjectorImpl.getProvider(InjectorImpl.java:693)
	at com.google.inject.InjectorImpl.getInstance(InjectorImpl.java:724)
	at demo.error.Error3.main(Error3.java:19)

Notice how Guice also links to the source configuration line (Error3.java:15), which is clickable in any Java IDE. Note that Guice can also bind enum values directly, which would then result in a compile error if you make a typo. Don't use string conversion when you don't have to.

Spring:

    <bean id="nu" class="demo.spring.xml.error.NumberUser">
        <!-- Typo -->
        <constructor-arg value="TW"/>
    </bean>

Spring Result:

Exception in thread "main" org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'nu' defined in class path resource [demo/spring/xml/error/error3.xml]: 
Unsatisfied dependency expressed through constructor argument with index 0 of type [demo.error.Number]: 
Could not convert constructor argument value of type [java.lang.String] to required type [demo.error.Number]:
Failed to convert value of type [java.lang.String] to required type [demo.error.Number]; 
nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [java.lang.String] to required type [demo.error.Number]: 
no matching editors or conversion strategy found
	at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:544)
	at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:190)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:893)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:803)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:437)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:404)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:375)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:263)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:170)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:260)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:184)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:163)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:430)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at demo.spring.xml.error.Error3.main(Error3.java:9)

Which basically tells you the world is about to end. At least, that is what I can make of it.

Four

Import non-existent configuration definitions from a configuration unit.

Guice:

public class Error4 {
    public static void main(String[] args) {
        Guice.createInjector(new AbstractModule() {
            protected void configure() {
                install(new MyModula());
            }
        });
    }
    
    static class MyModule implements Module {
        public void configure(Binder binder) {
            // whatever...
        }
    }
}

Guice Result:

Compile error.

Spring:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context-2.5.xsd">
                        
    <import resource="does_not_exist.xml"/>
</beans>

Spring Result (Added line breaks):

Exception in thread "main" org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: 
Failed to import bean definitions from relative location [does_not_exist.xml]
Offending resource: class path resource [demo/spring/xml/error/error4.xml];
nested exception is org.springframework.beans.factory.BeanDefinitionStoreException:
IOException parsing XML document from class path resource [demo/spring/xml/error/does_not_exist.xml]; 
nested exception is java.io.FileNotFoundException: class path resource [demo/spring/xml/error/does_not_exist.xml] cannot be opened because it does not exist
	at org.springframework.beans.factory.parsing.FailFastProblemReporter.error(FailFastProblemReporter.java:68)
	at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:85)
	at org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:76)
	at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.importBeanDefinitionResource(DefaultBeanDefinitionDocumentReader.java:201)
	at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseDefaultElement(DefaultBeanDefinitionDocumentReader.java:147)
	at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:132)
	at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:92)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:489)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:384)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:328)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:296)
	at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:143)
	at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:178)
	at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:149)
	at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:212)
	at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:113)
	at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:80)
	at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:123)
	at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:423)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:353)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at demo.spring.xml.error.Error4.main(Error4.java:9)
Caused by: org.springframework.beans.factory.BeanDefinitionStoreException: 
IOException parsing XML document from class path resource [demo/spring/xml/error/does_not_exist.xml]; nested exception is java.io.FileNotFoundException:
class path resource [demo/spring/xml/error/does_not_exist.xml] cannot be opened because it does not exist
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:335)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:296)
	at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.importBeanDefinitionResource(DefaultBeanDefinitionDocumentReader.java:190)
	... 19 more
Caused by: java.io.FileNotFoundException: class path resource [demo/spring/xml/error/does_not_exist.xml] cannot be opened because it does not exist
	at org.springframework.core.io.ClassPathResource.getInputStream(ClassPathResource.java:142)
	at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:322)
	... 21 more

Besides all the useless junk, this exception actually tells you what is going on. But this code blows up at run time, not at compile time.

Closing Comment

To see how Guice collects multiple errors and presents them to you all at once (instead of one at a time), take a look at this test in the Guice sources. Thanks to Bob for pointing me to this example.

Output looks like:

1) Error at demo.ErrorHandlingTest$BadScope.class(ErrorHandlingTest.java:1):
 Please annotate with @ScopeAnnotation.

2) Error at demo.ErrorHandlingTest$BadScope.class(ErrorHandlingTest.java:1):
 Please annotate with @Retention(RUNTIME). Bound at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:139).

3) Error at demo.ErrorHandlingTest$Bar.<init>(ErrorHandlingTest.java:96):
 Could not find a suitable constructor in demo.ErrorHandlingTest$Bar. Classes must have either one (and only one) constructor annotated with @Inject or a zero-argument constructor.

4) Error at demo.ErrorHandlingTest$Bar.bar(ErrorHandlingTest.java:100):
 Binding to java.lang.String annotated with @com.google.inject.name.Named(value=foo) not found. Annotations on other bindings to that type include: [@com.google.inject.name.Named(value=foo)]

5) Error at demo.ErrorHandlingTest$Bar.setNumbers(ErrorHandlingTest.java:98):
 Binding to java.util.List<java.lang.Integer> annotated with @com.google.inject.name.Named(value=numbers) not found. No bindings to that type were found.

6) Error at demo.ErrorHandlingTest$I.class(ErrorHandlingTest.java:1):
 java.lang.String doesn't extend demo.ErrorHandlingTest$I.

7) Error at demo.ErrorHandlingTest$Invalid.<init>(ErrorHandlingTest.java:112):
 Error while injecting at demo.ErrorHandlingTest$Tee.invalid(ErrorHandlingTest.java:103): Could not find a suitable constructor in demo.ErrorHandlingTest$Invalid. Classes must have either one (and only one) constructor annotated with @Inject or a zero-argument constructor.

8) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:136):
 No scope is bound to @Named.

9) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:137):
 Binding points to itself.

10) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:137):
 A binding to java.lang.Runnable was already configured at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:131).

11) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:147):
 I don't like you

12) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:153):
 An exception was caught and reported. See log for details. Message: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer

13) Error at demo.ErrorHandlingTest$MyModule.configure(ErrorHandlingTest.java:156):
 Binding to core guice framework type is not allowed: Module.

14) Error at demo.ErrorHandlingTest$Tee.tee(ErrorHandlingTest.java:106):
 Binding to int not found. No bindings to that type were found.

15) Error at demo.ErrorHandlingTest$TooManyScopes.class(ErrorHandlingTest.java:116):
 More than one scope annotation was found: @Singleton and @GoodScope

16) Error at demo.ErrorHandlingTest.missing(ErrorHandlingTest.java:44):
 Binding to java.util.List<java.lang.String> annotated with @com.google.inject.name.Named(value=missing) not found. Annotations on other bindings to that type include: [[no annotation]]

No more run-fix-run-fix-run-fix. Guice lets you run-fix-fix-fix. :-)