Spring inspired dependency injection for Incr Tcl.
###Dependency Injection Engine ('Bean Factory' in Spring terminology)
- load propertiesFile: Loads a plain text properties file to define all of the spring-like beans
- createObjectByName objectName: Creates an Incr tcl object from the bean definition
package require DependencyInjector 3.1
#instantiate the Dependency Injector
set di [DI::DependencyInjector #auto ]
#load the properties file
$di load myObjects.properties
set myClock [$di createObjectByName clock]>cd test/scripts
>tclsh ./all.tcl
Tests ended at Mon Jul 01 05:36:23 PM PDT 2013
all.tcl: Total 9 Passed 9 Skipped 0 Failed 0
Sourced 2 Test Files.
###Defining an Incr-tcl bean
The following two example Incr tcl classes both inherit from the Dhs::DependencyInjectionBean class. This class type will allow the DI engine to call the afterPrope rtiesSet method once the object has been constructed (this is similar to the InitializingBean in Spring). All public variables on the classes can be set from the co nfiguration file.
class Dhs::Clock {
inherit DCS::DependencyInjectionBean
public variable tickPeriodMs 200
public variable listeners
private variable totalSleepTimeMs 0
private variable initialTime 0
public method afterPropertiesSet {} {
set initialTime [clock seconds]
monitor
}
public method monitor {} {
foreach listener $listeners {
if { [catch {
$listener tick $totalSleepTimeMs [expr [clock seconds] - $initialTime]
} err ]} {
global errorInfo
puts $errorInfo
}
}
incr totalSleepTimeMs $tickPeriodMs
after [expr $tickPeriodMs] [list $this monitor]
}
}
class Dhs::ClockLogger {
inherit DCS::DependencyInjectionBean
public variable period 5000
public method tick {sleepTimeMs totalElapsedTimeS} {
if { [expr $sleepTimeMs % $period ] == 0 } {
puts "ElapsedTime: $totalElapsedTimeS s"
}
}
}##Defining objects (beans) in the config file.
Within the configuration file, classes are instantiated and public variables are configured using the following syntax:
beanName.propertyName=value
Some fixed properties are enclosed in (). They include:
- (class): The value contains the name of the class for the DI engine to instantiate from.
- (parent): The value contains the name of a different bean. The DI engine apply all of the properties from the parent bean onto this bean. Properties set on this bean will override the properties set by the parent.
- (singleton): value can be either true or false and indicates whether a new bean is created for each reference to this bean (false), or if the same object should be shared between many other beans references (true).
- (ref) modifier preceeding a value: instructs the DI engine to first create another object defined in the config file and then use this object as the property value.
- (list) modifier appended to property value: instructs the DI engine that the property values will be a space separated list of values, which can be (ref) objects.
In the following configuration file, two objects are defined: a clock and a clockLogger. The name of the object is defined by the author of the configuration file. Properties are set using the following syntax: beanName.propertyName=value
clock.(class)=Dhs::Clock
clock.tickPeriodMs=100
clock.listeners(list)=(ref)clockLoggerSlow (ref)clockLoggerFast
clockLoggerSlow.(class)=Dhs::ClockLogger
clockLoggerSlow.period=60000
clockLoggerFast.(class)=Dhs::ClockLogger
clockLoggerFast.period=1000
##Asserting value types on properties
It is possible to assert that the values on a property are set with the correct type be checking the values in the afterPropertiesSet method. There are three methods in the DependencyInjectionBean for value and type-checking.
- assertPropertyNotEmpty [optional list of valid values]
- ssertPropertyIsaClass propertyName className
- assertEachListMemberIsaClass propertyName {className className ..}
Example:
public method afterPropertiesSet {} {
assertPropertyIsaClass motor1 Dhs::MotorBase
assertPropertyIsaClass motor2 Dhs::MotorBase
assertPropertyIsaClass translation Dhs::MotorBase
assertPropertyNotEmpty MT [list -2.5 2.5 -2.0 2.0]
}###Factory Bean
A bean defined in the properties file with a (class) property of DI::BeanFactory will be populated with a bean returned by the BeanFactory's getObject method (not the BeanFactory object itself). The base DI::BeanFactory class takes a property, 'bean', which refers to another bean in the configuration file to be instantiated instead of the BeanFactory.
If a bean in the configuration file needs the BeanFactory object itself, then preceed the bean name of the factory with an ampersand. In this case, from the application code, call the 'getObject' method on the BeanFactory to generate new instances of beans without having access or knowledge of the configuration file.
The following is an example configuration from the test directory:
#factory bean tests
hondaFactory.(class)=DI::FactoryBean
hondaFactory.bean=honda
honda.(class)=Car
honda.(singleton)=false
honda.make=civic
honda.year=2013
mazdaFactory.(class)=DI::FactoryBean
mazdaFactory.bean=mazda3
mazda3.(class)=Car
mazda3.(singleton)=false
mazda3.make=mazda
mazda3.year=
Use the property '@import=filename.properties' to load additional properties from other files into the bean factory. The properties are loaded in the order that they appear in the file. Imported files may also import their own files which are loaded before the top import is completed. Files that have been previously imported are not imported again, which prevents endless recursive imports. Conflicts on properties are always resolved by allowing the latest property definition to overwrite previous definitions. It is strongly recommended to put all of the imports at the top of a property file.
Example:
@import=application.properties
@import=scripts.properties
@import=galil.properties
@import=standard-devices.properties
@import=microspec.properties
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