Freemarker格式化缩进文本，处理include指令与import指令

在使用include指令时，文本会顶格到最左边，没有缩进。

这篇文章使用了自定义指令处理内容缩进
http://yuanhuiwu.iteye.com/blog/1133067

本文使用了不同的实现方式(一个一个翻API，费了半天劲总算找到了)

/**
 * 增加缩进的格式化指令,由标签起始位置决定输出多少空格
 * 例如：
 * <@format>
 * <#include path="..." />
 * </@format>
 * 
 */
public class FormatDirective implements TemplateDirectiveModel {

	@Override
	public void execute(Environment env, @SuppressWarnings("rawtypes") Map params, TemplateModel[] loopVars, TemplateDirectiveBody body)
			throws TemplateException, IOException {
		FormatWriter writer = new FormatWriter(env.getOut(),
				env.getCurrentDirectiveCallPlace().getBeginColumn());
		body.render(writer);
	}
	
	private static class FormatWriter extends Writer {
		
		private Writer out;
		
		private char[] space;
		
		public FormatWriter(Writer out, int column) {
			this.out = out;
			this.space = new char[column];
			Arrays.fill(this.space, ' ');
		}

		@Override
		public void write(char[] cbuf, int off, int len) throws IOException {
			out.write(space);
			out.write(cbuf);
		}

		@Override
		public void flush() throws IOException {
			out.flush();
		}

		@Override
		public void close() throws IOException {
			out.close();
		}
		
	}
}