About "Some characters cannot be mapped using" GB2312 "character encoding. "The question

Today, when I was doing the project, I encountered a problem. Because it is done on the basis of others to change things, so, some things can not be in accordance with their own habits. For example, I created a project when I just built the set character encoding set as UTF-8, and the other people's project is not necessarily the case. Well, there's not much nonsense. The problem is as follows: a JSP page (with Java code in IT) has an encoding set of GB2312, and I modify the contents of the inside to let me save, a save will prompt "Some characters cannot be mapped using" GB2312 "character Encoding ... ". It is not possible to change the character set to change. Later, in the online search, the solution is as follows:

MyEclipse ------------Content Types---click Java Properties file , the bottom appears ' Default edcodng: ', change to UTF-8, then update.

After the change is done, Or not (at this point, my JSP page's encoding set is GB2312). Later, the encoding set was changed to UTF-8, resolving the