Allow to specify a default value on placeholder

[kazuki43zoo]

I want to support that allow to specify a default value on properties placeholder as follow:

<dataSource type="POOLED">
  <property name="username" value="${db.username:postgres}"/>
  <property name="password" value="${db.password:Postgres}"/>
</dataSource>

This solution has been supported by the Spring Framework , Logback, etc...
Note that : We should take to consider the : character has been used as placeholder key or used ternary operator(such as condition ? value_if_true : value_if_false) using OGNL. (for backward compatibility)

What do you think this enhancement ?

[kazuki43zoo]

For prototype see 241ba45. In this changes, I does not take to consider backward compatibility yet.

[kazuki43zoo]

I've updated the prototype via cbc6fe0. In this version, backward compatibility has been taken to consider.

By default this feature is disabled .
When using this feature, a special property will specify as follow:

<properties>
    <property name="org.apache.ibatis.parsing.PropertyParser.enable-default-value" value="true"/>
</properties>

[emacarron]

I like the feature @kazuki43zoo

+1

[kazuki43zoo]

@emacarron @eddumelendez

Thanks for your reaction !! I will submit a PR after adding some improvements.

[kazuki43zoo]

I've improved the prototype via 0f057c2.

In this change, support to customize a separator characters.
When customizing separator characters(default is ":"), a special property will specify as follow:

<properties>
    <property name="org.apache.ibatis.parsing.PropertyParser.enable-default-value" value="true"/>
    <property name="org.apache.ibatis.parsing.PropertyParser.default-value-separator" value="?:"/> <!-- ### Adding ### -->
</properties>

If ":" character has been used as placeholder key already, this mechanism is effective as follow:

<dataSource type="POOLED">
  <property name="username" value="${db:username?:postgres}"/>
  <property name="password" value="${db:password?:Postgres}"/>
</dataSource>

and If ternary operator has been used using OGNL in your sql already, this mechanism is effective as follow:

@Select("SELECT * FROM ${db:schema?:prod}.${tableName == null ? 'global_constants' : tableName}" ORDER BY ${orderByColumns})
List<SysConstant> findAll(@Param("tableName") String tableName, @Param("orderByColumns") String orderByColumns);

Note that : A default value can not specify to the parameter replacement variable (above example: ${orderByColumns}) on your sql. If you want to specify a default value on the parameter replacement variable, should be use the OGNL expression instead of (e.g. ${orderByColumns != null ? orderByColumns : 'id'}).

[harawata]

Looks like a handy feature. Thank you :)

[kazuki43zoo]

Hi @harawata , thanks for your reaction !! I will gh-853 merge at later.