Monday, 29 July 2013

Default implementation of spring util:map

The default imlementation of <util:map> is LinkedHashMap, but you can change it like it is described underneath:

Sunday, 21 July 2013

Groovy and WS

If you try to use Apache CXF, you can have problems with generated inner classes, that are not implemented in groovy.
You can use

Some groovy gotchas

  • groovy -e “println ‘Hello World’” - execute groovy code from comand line
  • groovy Example.groovy - run groovy code from the file Example.groovy
  • groovyc Example.groovy - compile groovy code from the file to the JVM class. Then you can run this code with JVM adding groovy libraries: java -classpath groovy-all.jar:. Example
  • groovysh - interactive command line shell
  • groovyConsole - interactive GUI shell
  • Arithmetic:
  • BigDecimal is used by default for number literal with fraction
  • Number literals without fraction are the smallest type that fits Integer, Long, BigInteger
  • Strings:
  • Single quoted is standard java String
  • Double quoted is GString (may contain groovy expressions, can be substring using [])
  • Tripple quoted are multiline strings
  • Slashy - no escaping needed - useful for regex
  • Operator overloading - operators map to specific methods f.e. + is same ad method add()
  • Method can be referenced as closure with .& operator
  • Closures has properties:
  • maximumNumberOfParameters - number of parameters provided to closure
  • parameterTypes - array of types of parameters
  • Collection methods: collect - as map in Scala and inject as foldLeft
  • Objects evaluate to false: null, empty collections, iterators, empty GStrings, numbers equals 0, non-matching regexp pattern matchers, everything else evaluete to true
  • == is treated as equals() in java but null safe. If objects implement Comparable then compareTo method is used
  • - for java ==
  • string.contains(gstring) is false due to internal equals method usage
  • Null-safe operator returns null without futher evaluation in case od null ?.
  • Elvis operator shorthand for returning default value ?:
  • Spaceship operator <=> which replace compareTo method
  • regexp operator ~ what creates a Pattern, =~ what creates Matcher, ==~ matching String against regexp
  • spread operator *. is a shorthand for Collection.collect(closure)
  • as operator transforms a variable to another type
  • xml support with classes MarkupBuilder and XmlParser
  • json suppert with JsonBuilder, JsonSlurper
  • Integrations with java:
  • Groovy shell - evaluates expressions in Java with passing in and out variables
  • GroovyClassLoader - parse and compile classes
  • Groovy Joint Compiler - compile all groovy and java sources. Allows circular dependencies between them, but on other layers
  • Spring Groovy Integration - beans can be defined by POGO with lang namespace
  • Changes between groovy and java:
  • this inside static method refers to class
  • do-while loops are not supperted
  • all exceptions are unchecked
  • inner classes are not allowed
  • Built-in AST Transformations: @Singleton, @Delegate, @TupleConstructor, @TimedInterrupt
  • @TypedChecked - analyze at compile-time
  • @CompileStatic - compile like javac compiler, no groovy dynamic features