The document discusses Spring Expression Language (SpEL), which is a powerful expression language for querying and manipulating objects in the Spring Framework. SpEL supports expressions, property access, method invocation, operators, and more. It can be used across Spring products and in XML configuration, annotations, and code. SpEL provides a simple and consistent way to access application objects and metadata.

1. Spring Framework - Expression Language
SPRING FRAMEWORK 3.0
Dmitry Noskov Spring Expression Language

2. What is SpEL?
 is a powerful expression language
 much like OGNL, Jboss EL, etc.
 supports querying and manipulating an object
graph at runtime
 can be used across all the products in the Spring
portfolio
 can be used outside of Spring
Spring Framework - Expression Language Dmitry Noskov

3. Features
 expressions
 accessing properties, arrays, etc.
 assignment
 method invocation
 collection selection & projection
 etc.
Spring Framework - Expression Language Dmitry Noskov

4. Fundamentals
 ExpressionParser
 Expression
 getValue
 setValue
 EvaluationContext
 root
 setVariable
 propertyAccessor
Spring Framework - Expression Language Dmitry Noskov

5. Expression access
 configuration XML / @Value
 #{expression}
 programming
 parser.parseExpression(“expression for root”)
 parser.parseExpression(“#expression for variable”)
 custom template
 parser.parseExpression(“it is #{expression}”)
Spring Framework - Expression Language Dmitry Noskov

6. Using SpEL
Spring Framework - Expression Language Dmitry Noskov

7. XML
<bean id="systemConfig" class="org.training.spel.SystemConfig">
<property name="operatingSystem"
value="#{systemProperties['os.name']}"/>
<property name="javaVersion"
value="#{systemProperties['java.vm.version']}"/>
</bean>
Spring Framework - Expression Language Dmitry Noskov

8. @Value
public class SystemConfig {
@Value("#{systemProperties['java.vm.version']}")
private String operatingSystem;
@Value("#{systemProperties['java.vm.version']}")
private String javaVersion;
}
Note: <context:annotation-config/>
Spring Framework - Expression Language Dmitry Noskov

9. Expressions
Spring Framework - Expression Language Dmitry Noskov

10. Literal expressions
ExpressionParser parser = new SpelExpressionParser();
parser.parseExpression("'Hello World'").getValue(String.class);
parser.parseExpression("6.0221415E+23").getValue(Double.class);
parser.parseExpression("0x7FFFFFFF").getValue(Integer.class);
parser.parseExpression("'2011/01/17'").getValue(Date.class);
parser.parseExpression("true").getValue();
parser.parseExpression("null").getValue();
Spring Framework - Expression Language Dmitry Noskov

11. Type conversion
 Converter
public interface Converter<S, T> {
T convert(S source);
}
 ConversionService
 http://static.springsource.org/spring/docs/3.0.x/spri
ng-framework-reference/html/validation.html#core-
convert
Spring Framework - Expression Language Dmitry Noskov

12. Object properties
 #{person.name}
 #{person.Name}
 #{person.getName()}
Spring Framework - Expression Language Dmitry Noskov

13. Collections
 #{list[0]}
 #{list[0].name}
 #{map[‘key’]}
Spring Framework - Expression Language Dmitry Noskov

14. Methods
 #{‘Some Text’.substring(0, 2)}
 #{‘Some Text’.startsWith(‘text’)}
 #{“variable.toString()”}
Spring Framework - Expression Language Dmitry Noskov

15. Relational operators
 #{5 == 5} or #{5 eq 5}
 #{‘black’ > ’block’} or #{‘black’ gt ‘block’}
 #{‘text’ instanceof T(int)}
 #{'5.00' matches '^-?d+(.d{2})?$'}
Spring Framework - Expression Language Dmitry Noskov

16. Arithmetic operators
 #{5 + 5}
 #{(5 + 5) * 2}
 #{17 / 5 % 3}
 #{‘Hello’ + ‘ ‘ + ‘world’}
Spring Framework - Expression Language Dmitry Noskov

17. Logical operators
 #{true or false}
 #{!true}
 #{not isUserInGroup(‘admin’)}
Spring Framework - Expression Language Dmitry Noskov

18. Assignment
SimpleBean dima = new SimpleBean("Dima", 26);
EvaluationContext context = new StandardEvaluationContext(dima);
parser.parseExpression("name").setValue(context, "Dmitry");
parser.parseExpression("age=27").getValue(context);
Spring Framework - Expression Language Dmitry Noskov

19. Type operator
 #{T(java.util.Date)}
 #{T(String)}
 #{T(int)}
 accessing static class members
 #{T(Math).PI}
 #{T(Math).random()}
Spring Framework - Expression Language Dmitry Noskov

20. instanceof
 #{‘text’ instanceof T(String)}
 #{27 instanceof T(Integer)}
 #{false instanceof T(Boolean)}
Spring Framework - Expression Language Dmitry Noskov

21. Constructor
 #{new org.training.spel.Person(‘Misha’, 28)}
 #{list.add(new org.training.spel.Person())}
Spring Framework - Expression Language Dmitry Noskov

22. Variable registration
Map<String, Person> map = new HashMap<String, Person>();
map.put("Dima", new Person("Dima", 27));
map.put("Anya", new Person("Anya", 23));
ExpressionParser parser = new SpelExpressionParser();
StandardEvaluationContext ctx = new StandardEvaluationContext();
ctx.setVariable("map", map);
ctx.setVariable("anya", "Anya");
parser.parseExpression("#map['Dima']").getValue(ctx);
parser.parseExpression("#map[#anya]").getValue(ctx);
Spring Framework - Expression Language Dmitry Noskov

23. If-then-else
 #{person.age>50 ? ‘Old’ : ‘Young’}
 #{person.name ? : ‘N/A’}
Spring Framework - Expression Language Dmitry Noskov

24. Safe navigation
 #{address.city?.name}
 #{person.name?.length()}
Spring Framework - Expression Language Dmitry Noskov

25. Collection selection
 select all
 #{list.?[age>20]}
 #{list.?[name.startsWith(‘D’)]}
 select first
 #{list.^[age>20]}
 select last
 #{list.$[getAge()>20]}
Spring Framework - Expression Language Dmitry Noskov

26. Collection projection
 select the names of all elements
 #{list.![name]}
 select the names length of all elements
 #{list.![name.length()]}
Spring Framework - Expression Language Dmitry Noskov

27. Functions
ExpressionParser parser = new SpelExpressionParser();
EvaluationContext context = new StandardEvaluationContext();
context.registerFunction("max", Collections.class.
getDeclaredMethod("max", new Class[]{Collection.class}));
parser.parseExpression("#max(#list.![age])").getValue(context);
Spring Framework - Expression Language Dmitry Noskov

28. Templating
ExpressionParser parser = new SpelExpressionParser();
String value = parser.parseExpression(
"Random number is #{T(java.lang.Math).random()}",
new TemplateParserContext()
).getValue(String.class);
But:
parser.parseExpression("#{#primes.?[#this>10]}", …)
Spring Framework - Expression Language Dmitry Noskov

29. #root and #this
 array of integer
list.addAll(Arrays.asList(2,3,5,7,11,13,17));
p.parseExpression("#list.?[#this>10]").getValue(context);
 list of age
List<Person> list = new ArrayList<Person>();
p.parseExpression("#list.![age].?[#this>20]").getValue(context);
Spring Framework - Expression Language Dmitry Noskov

30. Using root object
 unchanging
StandardEvaluationContext context = new
StandardEvaluationContext(new Person("Dima", 25));
parser.parseExpression("name").getValue(context);
 changing
parser.parseExpression("name").getValue(new Person("Dima", 27));
 cached context
StandardEvaluationContext context = new
StandardEvaluationContext(new Person("Dima", 25));
parser.parseExpression("name").getValue(context, person1);
parser.parseExpression("name").getValue(context, person2);
Spring Framework - Expression Language Dmitry Noskov

31. Access to Spring context
<bean id="simpleBean" class="org.training.spel.Person"
p:name="Misha" p:age="#{25+23}"/>
ApplicationContext context =
new ClassPathXmlApplicationContext("context.xml");
Person bean = context.getBean(Person.class);
ExpressionParser parser = new SpelExpressionParser();
StandardEvaluationContext evaluation =
new StandardEvaluationContext(context);
evaluation.addPropertyAccessor(new BeanFactoryAccessor());
parser.parseExpression("simpleBean").getValue(evaluation);
Spring Framework - Expression Language Dmitry Noskov

32. Wiring properties
 simple
@Value("#{systemProperties['locale']}")
private Locale locale;
 default
@Value("#{systemProperties['locale']?:'RU'}")
private Locale locale;
 selective
@Value("#{systemProperties['level']>2 ? gold : default}")
private AccountRepository repository;
Spring Framework - Expression Language Dmitry Noskov

33. Information
 Spring type conversion reference
http://static.springsource.org/spring/docs/3.0.x/spring-
framework-reference/html/validation.html#core-convert
 Spring EL reference
http://static.springsource.org/spring/docs/3.0.x/spring-
framework-reference/html/expressions.html
Spring Framework - Expression Language Dmitry Noskov

34. Questions
Spring Framework - Expression Language Dmitry Noskov

35. The end
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