### Question:
DefaultParameterHandler implements ParameterHandler { @Override public void setParameters(PreparedStatement ps) { ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId()); List<ParameterMapping> parameterMappings = boundSql.getParameterMappings(); if (parameterMappings != null) { for (int i = 0; i < parameterMappings.size(); i++) { ParameterMapping parameterMapping = parameterMappings.get(i); if (parameterMapping.getMode() != ParameterMode.OUT) { Object value; String propertyName = parameterMapping.getProperty(); if (boundSql.hasAdditionalParameter(propertyName)) { value = boundSql.getAdditionalParameter(propertyName); } else if (parameterObject == null) { value = null; } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) { value = parameterObject; } else { MetaObject metaObject = configuration.newMetaObject(parameterObject); value = metaObject.getValue(propertyName); } TypeHandler typeHandler = parameterMapping.getTypeHandler(); JdbcType jdbcType = parameterMapping.getJdbcType(); if (value == null && jdbcType == null) { jdbcType = configuration.getJdbcTypeForNull(); } try { typeHandler.setParameter(ps, i + 1, value, jdbcType); } catch (TypeException | SQLException e) { throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e); } } } } } DefaultParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql); @Override Object getParameterObject(); @Override void setParameters(PreparedStatement ps);  }### Answer:
@Test void setParametersThrowsProperException() throws SQLException { final MappedStatement mappedStatement = getMappedStatement(); final Object parameterObject = null; final BoundSql boundSql = mock(BoundSql.class); TypeHandler<Object> typeHandler = mock(TypeHandler.class); doThrow(new SQLException("foo")).when(typeHandler).setParameter(any(PreparedStatement.class), anyInt(), any(), any(JdbcType.class)); ParameterMapping parameterMapping = new ParameterMapping.Builder(mappedStatement.getConfiguration(), "prop", typeHandler).build(); List<ParameterMapping> parameterMappings = Collections.singletonList(parameterMapping); when(boundSql.getParameterMappings()).thenReturn(parameterMappings); DefaultParameterHandler defaultParameterHandler = new DefaultParameterHandler(mappedStatement, parameterObject, boundSql); PreparedStatement ps = mock(PreparedStatement.class); try { defaultParameterHandler.setParameters(ps); Assertions.fail("Should have thrown TypeException"); } catch (Exception e) { Assertions.assertTrue(e instanceof TypeException, "expected TypeException"); Assertions.assertTrue(e.getMessage().contains("mapping: ParameterMapping")); } }