Type
SmartParam operates with own types to provide decoding and encoding logic for Java classes. When query vector is formed, provided objects are translated encoded to string using type specification from level. On parameter evaluation, two string values are passed to matcher (if defined) - encoded query value and string pattern from parameter entry. Third argument is type of these values. This allows on writing matchers that compare decoded values or operate on specific type.
When match has been found and output submatrix is returned, types are used to encoded submatrix values to Java object instances so they can be returned using one of many output submatrix helper methods.
Type and holder
Each type implementation consists of two parts. One is Type itself, other is AbstractHolder. Type specifies encoding/decoding routines and actualy operates on holder, not raw value. Holder is a null-safe wrapper around raw value with multiple converting methods that, if implemented, allow to get contained value as Date, Number, String etc. This can be utilized to transparently assign different meanings/representations of held object class (ex. date can be represented as number of milliseconds).
Custom implementation
Depending on type, there are 3 different ways to create custom type. When total control is needed, you might need to implement it from scratch. For simple types, it's enough to implement decoding/encoding features.
All custom types should be annotated with org.smartparam.engine.annotated.annotations.Type
to enable automatic discovery.
Implementing from scratch
Implement org.smartparam.engine.core.type.ValueHolder class to create raw value holder.
Holder is responsible for containing and performing operations on raw value,
encapsulating any information about value state (is it null? is it comparable?).
It also has accessor methods that might return different representations of value,
for example Date can be represented as long by returning number of milliseconds.
You can extend org.smartparam.engine.core.type.AbstractValueHolder to get
default implementation for most of methods.
Implement org.smartparam.core.type.Type, interface responsible for encoding
and decoding string representation from/to concrete ValueHolder.
Implementing with AbstractType
Type has some methods that are very important performance-wise, but you might
not need to customize them. If you need a solid, default implementation extend
org.smartparam.engine.core.type.AbstractType. Using this method is preferred if
you want to keep control over ValueHolder.
Simple implementation
Most of the times you will need Type to contain a simple value object used widely
across the application. If so, extend org.smartparam.engine.core.type.SimpleType
which already provides default ValueHolder implementation.
Bundled types
Boolean
Stores boolean value. Decodes any value understood by Boolean.valueOf(str).
Integer
Stores Long value, which can be interpreted as long, String, Integer or BigDecimal.
Number
Stores BigDecimal value, which can be interpreted as BigDecimal, long, int, double or String. Can decode numbers with either . (dot) or , (comma) decimal separators.
Date
Stores Date object. When decoding, tries to guess format of date using following patterns:
- dd-MM-yyyy
- dd.MM.yyyy
- dd/MM/yyyy
- yyyy-MM-dd
- yyyy.MM.dd
- yyyy/MM/dd
String
Default type, stores plain string.