缓冲流

Filter:

@WebFilter(
        asyncSupported = true,
        description = "内容替换过滤器",
        filterName = "replaceFilter",
         urlPatterns = { "/*" },
        initParams = {
                @WebInitParam(name = "filePath", value = "replace_ZH.properties")
        }
)
public class ReplaceFilter implements Filter {
    private Properties propert = new Properties();
    public void init(FilterConfig filterConfig) throws ServletException {
        //通过filterConfig获得初始化文件名
        String filePath = filterConfig.getInitParameter("filePath");
        try {
            //导入资源文件
            propert.load(ReplaceFilter.class.getClassLoader()
                    .getResourceAsStream(filePath));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse)response;
        //实例化响应器包装类
        ResponseReplaceWrapper resp = new ResponseReplaceWrapper(res);
        chain.doFilter(request, resp);
        //缓存输出字符
        String outString = resp.getCharWriter().toString();
        //循环替换不合法的字符
        for(Object obj:propert.keySet()){
            String key = (String) obj;
            outString = outString.replace(key, propert.getProperty(key));
             System.out.println(outString);
        }
        //用原先的HttpServletResponse输出字符
        PrintWriter out = res.getWriter();
        out.write(outString);
    }
    public void destroy() {
    }
}

responseReplaceWrapper

package hx.edu;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;
public class ResponseReplaceWrapper extends HttpServletResponseWrapper {
    /*
    * CharArrayWriter 实现了以数组作为目标的输出流。CharArrayWriter 有两个构造函数：
        CharArrayWriter( )
        CharArrayWriter(int numChars)
    第一种形式，创建了一个默认长度的缓冲器。
    * 第二种形式，缓冲器长度由numChars指定。
    * 缓冲器保存在CharArrayWriter的buf 成员中。
    * 缓冲器大小在需要的情况下可以自动增长。
    * 缓冲器保持的 字符数 包含在CharArrayWriter的count 成员中。buf 和count 都是受保护的域。
 */
    private final CharArrayWriter charWriter = new CharArrayWriter();
    public ResponseReplaceWrapper(HttpServletResponse response) {
        //必须调用父类构造方法
        super(response);
    }
  @Override
    public PrintWriter getWriter() throws IOException {
        //返回字符数组Writer，缓存内容
        return new PrintWriter(charWriter);
    }
    public CharArrayWriter getCharWriter() {
        return charWriter;
    }
}