code: @Test public void testAttachments(){
    RpcContext context=RpcContext.getContext();
    Map<String,String> map=new HashMap<String,String>();
    map.put("_11","1111");
    map.put("_22","2222");
    map.put(".33","3333");
    context.setAttachments(map);
    Assert.assertEquals(map,context.getAttachments());
    Assert.assertEquals("1111",context.getAttachment("_11"));
    context.setAttachment("_11","11.11");
    Assert.assertEquals("11.11",context.getAttachment("_11"));
    context.setAttachment(null,"22222");
    context.setAttachment("_22",null);
    Assert.assertEquals("22222",context.getAttachment(null));
    Assert.assertNull(context.getAttachment("_22"));
    Assert.assertNull(context.getAttachment("_33"));
    Assert.assertEquals("3333",context.getAttachment(".33"));
    context.clearAttachments();
    Assert.assertNull(context.getAttachment("_11"));
  }
  