That old Spring magic has me in its SpEL
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Transcript of That old Spring magic has me in its SpEL
That old Spring magic has me in its SpEL
Craig Walls
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
About me
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
About me
• Java, Spring, and OSGi fanatic
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
About me
• Java, Spring, and OSGi fanatic
• Principal consultant with Improving Enterprises
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
About me
• Java, Spring, and OSGi fanatic
• Principal consultant with Improving Enterprises
• Author
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
About me
• Java, Spring, and OSGi fanatic
• Principal consultant with Improving Enterprises
• Author
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
• Introducing SpEL
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
• Introducing SpEL
• Using SpEL
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
• Introducing SpEL
• Using SpEL
• SpEL Essentials
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
• Introducing SpEL
• Using SpEL
• SpEL Essentials
• A few SpEL incantations
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Agenda
• Introducing SpEL
• Using SpEL
• SpEL Essentials
• A few SpEL incantations
• Q & A
3
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Download the examples
Approximately the same code...
http://spring.habuma.com/examples/SpEL-examples.zip
4
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Introducing SpEL
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
What is SpEL
6
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
What is SpEL
• New in Spring 3.0
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
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
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
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.
Using SpEL
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Configuring beans with SpEL (XML)
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Configuring beans with SpEL (XML)
<bean id="appConfigurer" class="com.habuma.spel.tests.Witch"> <property name="name" value="#{systemProperties['WITCH_NAME']}" /></bean>
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Configuring beans with SpEL (@Value)
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Configuring beans with SpEL (@Value)
@Componentpublic class Wizard { @Value("#{systemEnvironment['WIZARD_NAME']}") private String name;
// ...}
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Programming with SpEL
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Programming with SpEL
ExpressionParser parser = new SpelAntlrExpressionParser();
StandardEvaluationContext context = new StandardEvaluationContext(rootObject);
Expression ex = parser.parseExpression("witches.^[isWicked()]");
Witch wickedWitch = (Witch) ex.getValue(context);
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Essential SpEL
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Literal expressions
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Literal expressions
#{'abracadabra'}
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Literal expressions
#{'abracadabra'}
#{42}
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Literal expressions
#{'abracadabra'}
#{42} #{3.1415926}
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Literal expressions
#{'abracadabra'}
#{42} #{3.1415926}
#{1e4}
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Literal expressions
#{'abracadabra'}
#{true}
#{42} #{3.1415926}
#{1e4}
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Literal expressions
#{'abracadabra'}
#{true} #{false}
#{42} #{3.1415926}
#{1e4}
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Literal expressions
#{'abracadabra'}
#{true} #{false}
#{42} #{3.1415926}
#{null}
#{1e4}
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Ready-to-use variables
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Ready-to-use variables
#{systemProperties['WIZARD_NAME']}
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Ready-to-use variables
#{systemProperties['WIZARD_NAME']}
#{systemProperties.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']}
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
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Ready-to-use variables
#{request.getParameter('wizardId')}
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Ready-to-use variables
#{request.getParameter('wizardId')}
#{session.getAttribute('wizard')}
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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.
Constructors
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Constructors
#{new com.habuma.spel.tests.Wizard('Gandalf')}
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Constructors
#{new com.habuma.spel.tests.Wizard('Gandalf')}
#{new String('hokus pokus')}
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Accessing object members
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Accessing object members
#{elf.name}
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Accessing object members
#{elf.name}
#{elf.Name}
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Accessing object members
#{elf.name}
#{elf.Name}
#{elf.getName()}
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Accessing object members
#{elf.name}
#{elf.Name}
#{elf.getName()}
#{elf.name?.length()}
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Mixing expressions and text
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Mixing expressions and text
The wizard’s name is #{wizard.name}
Embeds the wizard’s name in some text
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Arithmetic operators
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
#{25 + 52}
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
#{25 + 52} #{2.19 + 2.02}
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
#{25 + 52} #{2.19 + 2.02}
#{77 - 25}
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
#{25 + 52} #{2.19 + 2.02}
#{77 - 25} #{52 - -25}
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Arithmetic operators
#{'Harry' + ' ' + 'Potter'}
#{25 + 52} #{2.19 + 2.02}
#{77 - 25} #{52 - -25}
#{6 * 7}
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}
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}
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Relational operators
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Relational operators
#{42 > 7}
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Relational operators
#{42 > 7} #{7 > 42}
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Relational operators
#{42 > 7} #{7 > 42}
#{10000 == 1e4}
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Relational operators
#{42 > 7} #{7 > 42}
#{10000 == 1e4}
#{‘Apple’ == ‘Apple’}
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Relational operators
#{42 > 7} #{7 > 42}
#{10000 == 1e4}
#{‘Apple’ == ‘Apple’}
#{‘Apple’ < ‘Orange’}
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’}
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Logical operators
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Logical operators
#{witch.isWicked() and witch.name == 'Elphaba'}
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Logical operators
#{witch.isWicked() and witch.name == 'Elphaba'}
#{witch.isWicked() or witch.name == 'Tattypoo'}
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Logical operators
#{witch.isWicked() and witch.name == 'Elphaba'}
#{witch.isWicked() or witch.name == 'Tattypoo'}
#{!witch.isWicked()}
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Ternary and Elvis operator
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Ternary and Elvis operator
#{wizard.isGood() ? 'Gandalf' : 'Saruman'}
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Ternary and Elvis operator
#{wizard.isGood() ? 'Gandalf' : 'Saruman'}
#{wizard.name ?: 'unknown'}
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The type operator : T()
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The type operator : T()
#{T(String)}
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The type operator : T()
#{T(String)}
#{T(Math)}
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The type operator : T()
#{T(String)}
#{T(Math)}
#{T(int)}
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The type operator : T()
#{T(String)}
#{T(Math)}
#{T(int)}
#{T(java.util.Date)}
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Accessing class members
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Accessing class members
#{T(Math).floor(42.56)}
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Accessing class members
#{T(Math).floor(42.56)}
#{T(Math).PI}
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instanceof
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instanceof
#{‘Sabrina’ instanceof T(String)}
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instanceof
#{‘Sabrina’ instanceof T(String)}
#{123 instanceof T(Integer)}
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instanceof
#{‘Sabrina’ instanceof T(String)}
#{123 instanceof T(Integer)}
#{123L instanceof T(Long)}
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instanceof
#{‘Sabrina’ instanceof T(String)}
#{123 instanceof T(Integer)}
#{123L instanceof T(Long)}
#{1.23 instanceof T(Double)}
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instanceof
#{‘Sabrina’ instanceof T(String)}
#{123 instanceof T(Integer)}
#{123L instanceof T(Long)}
#{true instanceof T(Boolean)}
#{1.23 instanceof T(Double)}
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Regular expressions
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Regular expressions
#{phoneNumber matches '\\d{3}-\\d{3}-\\d{4}'}
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Regular expressions
#{phoneNumber matches '\\d{3}-\\d{3}-\\d{4}'}
#{websiteUrl matches 'http://www\\.[a-zA-Z0-9]*\\.(com|edu|net)'}
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Regular expressions
#{phoneNumber matches '\\d{3}-\\d{3}-\\d{4}'}
#{customerEmail matches '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4}'}
#{websiteUrl matches 'http://www\\.[a-zA-Z0-9]*\\.(com|edu|net)'}
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Setting variables
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Setting variables
Assuming that the root object has a name property...
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Setting variables
name = 'Broomhilda'
Assuming that the root object has a name property...
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Accessing collection members
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Accessing collection members
#{wizards[0]}
Arrays
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Accessing collection members
#{wizards[0]}
#{magicWords['abracadabra']}
Arrays
Maps and Properties
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Collection selection
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Collection selection
#{witches.?[!isWicked()]}
Select all witches that aren’t wicked
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Collection selection
#{witches.?[!isWicked()]}
#{witches.^[isWicked()]}
Select all witches that aren’t wicked
Select the first wicked witch
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Collection selection
#{witches.?[!isWicked()]}
#{witches.^[isWicked()]}
#{witches.$[isWicked()]}
Select all witches that aren’t wicked
Select the first wicked witch
Select the last wicked witch
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Collection projection
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Collection projection
#{wizards.![name]}
Get the names of all wizards
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The #this variable
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The #this variable
#{wizards.![name].?[#this > 'G']}
Get the names of all wizards whose name is lexically ordered after ‘G’
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Adding a custom function
31
Only available with programmatic SpEL
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Adding a custom function
31
context = new StandardEvaluationContext();parser = new SpelAntlrExpressionParser();context.registerFunction("inEnglish", EnglishNumberInator.class.getDeclaredMethod( "translate", new Class[] {int.class}));
Only available with programmatic SpEL
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Adding a custom function
31
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);
Only available with programmatic SpEL
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Demo
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A few SpEL incantations
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Wiring in a system property (with a default)
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Wiring in a system property (with a default)
<bean class="Wizard"> <property name="name" value= "#{systemProperties['WIZARD_NAME'] ?: 'Gandalf'}" /></bean>
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Wiring bean references
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Wiring bean references
@Value("#{pricingService}")private PricingService pricingService;
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Wiring bean references
@Value("#{pricingService}")private PricingService pricingService;
<property name="pricingService" value="#{pricingService}" />
...or...
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Wiring bean references
@Value("#{pricingService}")private PricingService pricingService;
<property name="pricingService" value="#{pricingService}" />
Don’t do this!
...or...
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Wiring bean references
@Value("#{pricingService}")private PricingService pricingService;
<property name="pricingService" value="#{pricingService}" />
Don’t do this!However...
...or...
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Selective bean wiring
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Selective bean wiring
@Value("#{systemProperties['PRICING'] == 'aggressive'" + "? aggressivePricing : regularPricing}")private PricingService pricingService;
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Selective collection wiring
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Selective collection wiring
public interface TaxRule { boolean appliesToState(String state); double calculateTax(double base);}
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Selective collection wiring
public interface TaxRule { boolean appliesToState(String state); double calculateTax(double base);}
<util:list id="taxRules"> <ref id="revenueTax" /> <ref id="carpetTax" /> <ref id="existenceTax" /> <ref id="justBecauseTax" /></util:list>
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Selective collection wiring
<bean id="taxProcessor" class="TaxProcessor" scope="session"> <aop:scoped-proxy /> <property name="taxRules" value= "#{taxRules.?[appliesToState(session.getAttribute('user').state)]}" /></bean>
public interface TaxRule { boolean appliesToState(String state); double calculateTax(double base);}
<util:list id="taxRules"> <ref id="revenueTax" /> <ref id="carpetTax" /> <ref id="existenceTax" /> <ref id="justBecauseTax" /></util:list>
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Parting thoughts
38
SpringOne 2GX 2009. All rights reserved. Do not distribute without permission.
Parting thoughts
• SpEL expressions are great for doing Spring configuration magic
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.
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.
Q&A
Thank you!Don’t forget to turn in your evaluations!!!