SpringMVC中CharacterEncodingFilter爲會在HiddenHttpMethodFilter之前

對於過濾器來說，就是在第一次請求前就要過濾條件，比如登錄條件過濾，亂碼過濾、HTTP請求過濾，但是對於這個只知道先過濾字符亂碼然後其他，那麼爲什麼要這麼做呢！我們可以從源碼中看到問題的實質

• CharacterEncodingFilter（通過構造方法來設置傳入的字符集）

public class CharacterEncodingFilter extends OncePerRequestFilter {

	@Nullable
	private String encoding;

	private boolean forceRequestEncoding = false;

	private boolean forceResponseEncoding = false;


	/**
	 * Create a default {@code CharacterEncodingFilter},
	 * with the encoding to be set via {@link #setEncoding}.
	 * @see #setEncoding
	 */
	public CharacterEncodingFilter() {
	}

	/**
	 * Create a {@code CharacterEncodingFilter} for the given encoding.
	 * @param encoding the encoding to apply
	 * @since 4.2.3
	 * @see #setEncoding
	 */
	public CharacterEncodingFilter(String encoding) {
		this(encoding, false);
	}
	public void setEncoding(@Nullable String encoding) {
		this.encoding = encoding;
	}
@Override
	protected void doFilterInternal(
			HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		String encoding = getEncoding();
		if (encoding != null) {
			if (isForceRequestEncoding() || request.getCharacterEncoding() == null) {
				request.setCharacterEncoding(encoding);
			}
			if (isForceResponseEncoding()) {
				response.setCharacterEncoding(encoding);
			}
		}
		filterChain.doFilter(request, response);
	}

• HiddenHttpMethodFilter，這個一上來就要了一個method並沒有設置字符集什麼的，如果這個在前，那麼必定會發生亂碼

@Override
	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		HttpServletRequest requestToUse = request;

		if ("POST".equals(request.getMethod()) && request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) == null) {
			String paramValue = request.getParameter(this.methodParam);
			if (StringUtils.hasLength(paramValue)) {
				requestToUse = new HttpMethodRequestWrapper(request, paramValue);
			}
		}

		filterChain.doFilter(requestToUse, response);
	}

所以必須先寫CharacterEncodingFilter再寫HiddenHttpMethodFilter