Add support method for generating dynamic sql on SQL class

[kazuki43zoo]

I propose to add following new method for generating dynamic sql on SQL.

• applyIf (similar <if> element in XML language driver)
• applyForEach (similar <foreach> element in XML language driver)

In this change, the developer can write dynamic sql using with fluent style as follow:

applyIf

// Generate following SQL if b and c is null
// UPDATE test SET a=#{a} WHERE (id=#{id})
String sqlString = new SQL()
  .UPDATE("test")
  .applyIf(bean::hasA, sql -> sql.SET("a=#{a}"))
  .applyIf(bean::hasB, sql -> sql.SET("b=#{b}"))
  .applyIf(bean::hasC, sql -> sql.SET("c=#{c}"))
  .WHERE("id=#{id}")
  .toString();

applyForEach

// Generate following SQL if beans has two element
// INSERT INTO test (a, b, c) VALUES (#{list[0].a}, #{list[0].b}, #{list[0].c}), (#{list[1].a}, #{list[1].b}, #{list[1].c})
String sqlString = new SQL()
  .INSERT_INTO("test")
  .INTO_COLUMNS("a", "b", "c")
  .applyForEach(beans, (sql, element, index) ->
    sql.INTO_VALUES(
      String.format("#{list[%s].a}", index),
      String.format("#{list[%s].b}", index),
      String.format("#{list[%s].c}", index)
    ).ADD_ROW())
  .toString();

@mybatis/committers WDYT?

[coveralls]

coverage: 87.559% (+0.01%) from 87.545% when pulling bc050f2 on kazuki43zoo:add-suport-method-for-generating-dynamic-sql-on-SQL into c060395 on mybatis:master.

[hazendaz]

@harawata Thoughts? LGTM. Forgot about this.

[harawata]

@hazendaz @kazuki43zoo

Looks handy. Thank you!

[hazendaz]

@kazuki43zoo Can you update the at since? Then feel free to merge it.

[hazendaz]

merging and fill fix since right after.