对于servlet转发后乱码的一个可能原因

昨天开始做的BLOG系统，今天快要完工了，但是，突然碰见了一个校问题，那就是，在servlet中用request.getRequestDispatcher("../singleList.jsp").forward(request, response);转向到JSP页面后竟然发生了乱码问题，乱码问题是很常见的，不过这样出现也有点奇怪，后来处理了一下，怎么弄都是有问题。最后才发现，原来因为在servlet里面多写下了这么一句话PrintWirter out = esponse.getWriter();这句话是ECLIPSE自动生成的，因为没有用，我忘给删掉了。结果，正是他对我的程序编码产生了影响。

以下测试程序：
import java.io.IOException; import java.io.PrintWriter; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class TestServlet extends HttpServlet { @Override public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { // PrintWriter out = response.getWriter(); // 关键在这一句，如果有，则会出现乱码的。 RequestDispatcher requestDispatcher = request.getRequestDispatcher("/test/test2.jsp"); requestDispatcher.forward(request, response); } }

曾经尝试增加如下语句，问题依然存在

package test; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class TestServlet extends HttpServlet ...{ @Override public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException ...{ PrintWriter out = response.getWriter(); response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); RequestDispatcher requestDispatcher = request.getRequestDispatcher("/test/test2.jsp"); requestDispatcher.forward(request, response); } }
去掉后，就可以正常显示汉字了，
经多次测试，发现是语句的顺序有问题，需要调整为如下的代码即可
package test; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class TestServlet extends HttpServlet ...{ @Override public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException ...{ response.setCharacterEncoding("UTF-8"); // 先指定输出流的编码 PrintWriter out = response.getWriter(); // 再拿到输出对象 response.setContentType("text/html;charset=UTF-8"); RequestDispatcher requestDispatcher = request.getRequestDispatcher("/test/test2.jsp"); requestDispatcher.forward(request, response); } }

总结：response.getWriter() 在内部的实现上，影响了输出结果的编码集。必须先指定编码集，在调用Writer才可以。