Placeholders for prepared parameters are expanded too early

[sbernatsky]

I have a mapper which passes prepared parameters into velocity macro. And this fails for at least two cases:

• When parameters in macro are used in different order than they are defined in the macro;
• When parameters are used more than one time in macro.

Most probably is is due to the changes in velocity from version 2.0 where they changed when arguments are evaluated (https://velocity.apache.org/engine/2.4.1/upgrading.html#vtl-changes_3):

Velocimacro arguments are now evaluated only once (instead of each time they were referenced inside the macro body as was the case for v1.7) and passed by value (or more precisely as reference after evaluation).

Using parameters in other order than they are defined

Mapper:

<select id="selectFromMacroParamsOrder" resultType="org.mybatis.scripting.velocity.use.Name">
  #macro(select_values $firstName, $lastName)
    SELECT firstName, lastName FROM (VALUES ($lastName, $firstName)) as tmp (lastName, firstName)
  #end
  #select_values(@{firstName}, @{lastName})
</select>

Test:

  @Test
  public void testSelectFromMacroWithParametersOrdering() {
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {

      Name fred = new Name();
      fred.setFirstName("Fred");
      fred.setLastName("Flinstone");

      List<Name> answers = sqlSession.selectList("org.mybatis.scripting.velocity.use.selectFromMacroParamsOrder", fred);
      assertEquals(1, answers.size());
      assertEquals(answers.get(0).getFirstName(), fred.getFirstName());
      assertEquals(answers.get(0).getLastName(), fred.getLastName());
    }
  }

MyBatis mapper logs:

[main] DEBUG org.mybatis.scripting.velocity.use.selectFromMacroParamsOrder - ==>  Preparing: SELECT firstName, lastName FROM (VALUES (?, ?)) as tmp (lastName, firstName)
[main] DEBUG org.mybatis.scripting.velocity.use.selectFromMacroParamsOrder - ==> Parameters: Fred(String), Flinstone(String)
[main] DEBUG org.mybatis.scripting.velocity.use.selectFromMacroParamsOrder - <==      Total: 1

Using parameters more than once in macro

Mapper:

<select id="selectFromMacroMultipleTimes" resultType="java.lang.String">
  #macro(select_multiple $value)
    SELECT * FROM (VALUES ($value), ($value)) as tmp (v)
  #end
  #select_multiple(@{value})
</select>

Test:

  @Test
  public void testSelectFromMacroMultipleTimes() {
    try (SqlSession sqlSession = sqlSessionFactory.openSession()) {

      List<String> answers = sqlSession.selectList("org.mybatis.scripting.velocity.use.selectFromMacroMultipleTimes", "A");
      assertEquals(2, answers.size());
      assertEquals(answers.get(0), "A");
      assertEquals(answers.get(1), "A");
    }
  }

MyBatis mapper logs:

[main] DEBUG org.mybatis.scripting.velocity.use.selectFromMacroMultipleTimes - ==>  Preparing: SELECT * FROM (VALUES (?), (?)) as tmp (v)
[main] DEBUG org.mybatis.scripting.velocity.use.selectFromMacroMultipleTimes - ==> Parameters: A(String)

Probably the ParameterMappingCollector should return some 'proxy' from org.mybatis.scripting.velocity.ParameterMappingCollector.g(int) method, which would add parameter mapping on toString call.

[sbernatsky]

Following quick changes to ParameterMappingCollector class fix tests from above:

  private class Placeholder {
    private final ParameterMapping parameterMapping;

    public Placeholder(ParameterMapping parameterMapping) {
      this.parameterMapping = parameterMapping;
    }

    @Override
    public String toString() {
      parameterMappings.add(parameterMapping);
      return "?";
    }
  }

  public Object g(int mapping) {
    ParameterMapping parameterMapping = this.parameterMappingSources[mapping];
    PropertyInfo vi = getPropertyInfo(parameterMapping.getProperty());
    if (vi.isIterable) {
      parameterMapping = itemize(parameterMapping, vi);
      this.context.put(vi.root, this.context.get(this.itemKey));
    }
    // this.parameterMappings.add(parameterMapping);
    return new Placeholder(parameterMapping);
  }