That old Spring magic has me in its SpEL

That old Spring magic has me in its SpEL Craig Walls

What is SpEL • New in Spring 3.0 – Originally conceived in Spring.NET • The Spring Expression Language • Much like Unified EL, OGNL, JBoss EL, and others 6 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

What is SpEL • New in Spring 3.0 – Originally conceived in Spring.NET • The Spring Expression Language • Much like Unified EL, OGNL, JBoss EL, and others • Will be used across entire Spring portfolio 6 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

What is SpEL • New in Spring 3.0 – Originally conceived in Spring.NET • The Spring Expression Language • Much like Unified EL, OGNL, JBoss EL, and others • Will be used across entire Spring portfolio • Succinctly express complex concepts 6 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

What is SpEL • New in Spring 3.0 – Originally conceived in Spring.NET • The Spring Expression Language • Much like Unified EL, OGNL, JBoss EL, and others • Will be used across entire Spring portfolio • Succinctly express complex concepts • Can be used to wire bean properties 6 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

What is SpEL • New in Spring 3.0 – Originally conceived in Spring.NET • The Spring Expression Language • Much like Unified EL, OGNL, JBoss EL, and others • Will be used across entire Spring portfolio • Succinctly express complex concepts • Can be used to wire bean properties • Can be used outside of Spring 6 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Configuring beans with SpEL (XML) <bean id="appConﬁgurer" class="com.habuma.spel.tests.Witch"> <property name="name" value="#{systemProperties['WITCH_NAME']}" /> </bean> SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Configuring beans with SpEL (@Value) @Component public class Wizard { @Value("#{systemEnvironment['WIZARD_NAME']}") private String name; // ... } SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Programming with SpEL ExpressionParser parser = new SpelAntlrExpressionParser(); StandardEvaluationContext context = new StandardEvaluationContext(rootObject); Expression ex = parser.parseExpression("witches.^[isWicked()]"); Witch wickedWitch = (Witch) ex.getValue(context); SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Ready-to-use variables #{systemProperties['WIZARD_NAME']} #{systemProperties.WIZARD_NAME} #{systemEnvironment['WIZARD_NAME']} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Ready-to-use variables #{systemProperties['WIZARD_NAME']} #{systemProperties.WIZARD_NAME} #{systemEnvironment['WIZARD_NAME']} #{systemEnvironment.WIZARD_NAME} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Ready-to-use variables #{systemProperties['WIZARD_NAME']} #{systemProperties.WIZARD_NAME} #{systemEnvironment['WIZARD_NAME']} #{systemEnvironment.WIZARD_NAME} #{wizardBean.name} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Ready-to-use variables #{systemProperties['WIZARD_NAME']} #{systemProperties.WIZARD_NAME} #{systemEnvironment['WIZARD_NAME']} #{systemEnvironment.WIZARD_NAME} #{wizardBean.name} Only available when using SpEL in Spring configuration SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Ready-to-use variables #{request.getParameter('wizardId')} #{session.getAttribute('wizard')} Can only be used to configure appropriately-scoped beans SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Arithmetic operators #{'Harry' + ' ' + 'Potter'} #{25 + 52} #{2.19 + 2.02} #{77 - 25} #{52 - -25} #{6 * 7} #{42 / 6} #{44 % 7} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Relational operators #{42 > 7} #{7 > 42} #{10000 == 1e4} #{‘Apple’ == ‘Apple’} #{‘Apple’ < ‘Orange’} #{‘Orange’ > ‘Apple’} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Logical operators #{witch.isWicked() and witch.name == 'Elphaba'} #{witch.isWicked() or witch.name == 'Tattypoo'} #{!witch.isWicked()} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

instanceof #{‘Sabrina’ instanceof T(String)} #{123 instanceof T(Integer)} #{123L instanceof T(Long)} #{1.23 instanceof T(Double)} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

instanceof #{‘Sabrina’ instanceof T(String)} #{123 instanceof T(Integer)} #{123L instanceof T(Long)} #{1.23 instanceof T(Double)} #{true instanceof T(Boolean)} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Regular expressions #{phoneNumber matches 'd{3}-d{3}-d{4}'} #{websiteUrl matches 'http://www.[a-zA-Z0-9]*.(com|edu|net)'} #{customerEmail matches '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,4}'} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Collection selection Select all witches that aren’t wicked #{witches.?[!isWicked()]} Select the first wicked witch #{witches.^[isWicked()]} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Collection selection Select all witches that aren’t wicked #{witches.?[!isWicked()]} Select the first wicked witch #{witches.^[isWicked()]} Select the last wicked witch #{witches.$[isWicked()]} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

The #this variable Get the names of all wizards whose name is lexically ordered after ‘G’ #{wizards.![name].?[#this > 'G']} SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Adding a custom function Only available with programmatic SpEL context = new StandardEvaluationContext(); parser = new SpelAntlrExpressionParser(); context.registerFunction("inEnglish", EnglishNumberInator.class.getDeclaredMethod( "translate", new Class[] {int.class})); 31 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Adding a custom function Only available with programmatic SpEL context = new StandardEvaluationContext(); parser = new SpelAntlrExpressionParser(); context.registerFunction("inEnglish", EnglishNumberInator.class.getDeclaredMethod( "translate", new Class[] {int.class})); Expression ex = parser.parseExpression("#inEnglish(123)"); String englishNumber = ex.getValue(context); 31 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Wiring in a system property (with a default) <bean class="Wizard"> <property name="name" value= "#{systemProperties['WIZARD_NAME'] ?: 'Gandalf'}" /> </bean> SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Wiring bean references @Value("#{pricingService}") private PricingService pricingService; ...or... <property name="pricingService" value="#{pricingService}" /> SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Wiring bean references @Value("#{pricingService}") private PricingService pricingService; ...or... <property name="pricingService" value="#{pricingService}" /> Don’t do this! SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Wiring bean references @Value("#{pricingService}") private PricingService pricingService; ...or... <property name="pricingService" value="#{pricingService}" /> Don’t do this! However... SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Selective bean wiring @Value("#{systemProperties['PRICING'] == 'aggressive'" + "? aggressivePricing : regularPricing}") private PricingService pricingService; SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Selective collection wiring public interface TaxRule { boolean appliesToState(String state); double calculateTax(double base); } SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Selective collection wiring <util:list id="taxRules"> public interface TaxRule { <ref id="revenueTax" /> boolean appliesToState(String state); <ref id="carpetTax" /> double calculateTax(double base); <ref id="existenceTax" /> } <ref id="justBecauseTax" /> </util:list> SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Selective collection wiring <util:list id="taxRules"> public interface TaxRule { <ref id="revenueTax" /> boolean appliesToState(String state); <ref id="carpetTax" /> double calculateTax(double base); <ref id="existenceTax" /> } <ref id="justBecauseTax" /> </util:list> <bean id="taxProcessor" class="TaxProcessor" scope="session"> <aop:scoped-proxy /> <property name="taxRules" value= "#{taxRules.?[appliesToState(session.getAttribute('user').state)]}" /> </bean> SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Parting thoughts • SpEL expressions are great for doing Spring configuration magic • SpEL expressions are just Strings...no compile- time help to ensure type-safety, syntax, etc. 38 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Parting thoughts • SpEL expressions are great for doing Spring configuration magic • SpEL expressions are just Strings...no compile- time help to ensure type-safety, syntax, etc. • Don’t abuse SpEL 38 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Parting thoughts • SpEL expressions are great for doing Spring configuration magic • SpEL expressions are just Strings...no compile- time help to ensure type-safety, syntax, etc. • Don’t abuse SpEL – Remember Goethe’s Sorcerer’s Apprentice 38 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Parting thoughts • SpEL expressions are great for doing Spring configuration magic • SpEL expressions are just Strings...no compile- time help to ensure type-safety, syntax, etc. • Don’t abuse SpEL – Remember Goethe’s Sorcerer’s Apprentice – A little bit of magic in the wrong hands can be dangerous 38 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

Parting thoughts • SpEL expressions are great for doing Spring configuration magic • SpEL expressions are just Strings...no compile- time help to ensure type-safety, syntax, etc. • Don’t abuse SpEL – Remember Goethe’s Sorcerer’s Apprentice – A little bit of magic in the wrong hands can be dangerous • Write tests!!! 38 SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.

That old Spring magic has me in its SpEL

by Craig Walls

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