Converters

Overview

Converters take string instances in PicoContainer and convert the type that a particular component requires for injection.  DefaultPicoContainer has built in converter for primitives:

  • Integer
  • Double
  • Boolean
  • Long
  • Float
  • Character
  • Byte
  • Short
  • File

Integration Example

Here's a test case demonstrating a simple usage of converters

    public static class ConverterSample {
        public final int value;

        public ConverterSample(Integer value) {
            this.value = value;
        }
    }
    
    @Test
    public void testIntegrationWithConverters() {        
        MutablePicoContainer mpc = new DefaultPicoContainer();
        
        mpc.addComponent("converterParameter", "42")
            .addComponent(ConverterSample.class, ConverterSample.class, 
                    new ComponentParameter("converterParameter"));
					
        ConverterSample result = mpc.getComponent(ConverterSample.class);
        assertEquals(42, result.value);
    }

Custom Converters

You can extend BuiltInConverter, or implement the Converter interface directly.  BuiltInConverter has a method addConverter(..) which you may find convenient: 

BuiltInConverters bic = new
BuiltInConverters();
bic.addConverter(new SomeCustomThingConverter(), SomeCustomThing.class);

Alternatively, you can subclass BuildInConverters: 

BuiltInConverters bic = new BuiltInConverters() {
    @Override
    protected void addBuiltInConverters() {
        super.addBuiltInConverters();
        super.addConverter(new SomeCustomThingConverter(), SomeCustomThing.class);
    }
 };

or:

BuiltInConverters bic = new BuiltInConverters() {
    public BuiltInConverters() {
        super.addConverter(new SomeCustomThingConverter(), SomeCustomThing.class);
    }
};

Converters themselves are easy to write.  Here's the built in one for boolean:

class BooleanConverter implements Converter>Boolean<{
    public Boolean convert(String paramValue) {
        return Boolean.valueOf(paramValue);
    }
}

Setup a container to use your converter:

	MutableContainer pico = new DefaultPicoContainer() {
    @Override
    public ConverterSet getConverter() {
        return new BuildInConverters() {
			public BuiltInConverters() {
				super.addConverter(new SomeCustomThingConverter(), SomeCustomThing.class);
			}			
		}
    }
};