java 请求响应乱码

package org.operamasks.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONArray;

import org.operamasks.data.TreeNode;
import org.operamasks.data.TreeNodeService;

public class OmTreeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,
            IOException {
        doPost(request, response);
    }
    
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    	
    	request.setCharacterEncoding("UTF-8");
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html");
		String method = request.getParameter("method");
		String content = request.getParameter("content");
		if("position".equals(method)){
			getPositon(request, response);
		}else if("children".equals(content)){
			getChildren(request, response);
		}else if("simpleModel".equals(method)){
			getSimpleModel(request, response);
		}
		else{
			PrintWriter writer =  response.getWriter();
	        String result = 
	        "["+
	         "{"text": "Folder 1"," +
	             ""expanded": true," +
	             ""children":" +
	             "[" +
	                 "{"+
	                     ""text": "file 1.1"" +
	                 "}," +
	                 "{" +
	                     ""text": "file 1.2"" +
	                 "}" +
	             "]" +
	         "}," +
	         "{" +
	             ""text": "Folder 2"," +
	             ""hasChildren": true" +
	         "}," +
	         "{" +
	             ""text": "file 3"" +
	         "}" +
	     "]";
	        writer.write(result.toString());
	        writer.flush();
		}
    }

	private void getSimpleModel(HttpServletRequest request,
			HttpServletResponse response) throws IOException {
		// TODO Auto-generated method stub
		PrintWriter writer = response.getWriter();
		TreeNodeService service =new TreeNodeService();
		List<TreeNode> nodes = service.getNodes();
		writer.write(JSONArray.fromObject(nodes).toString());
		
	}

	private void getChildren(HttpServletRequest request,
			HttpServletResponse response) throws IOException {
		PrintWriter writer =  response.getWriter();
        String result = 
        "["+
         "{"text": "file 2.1"" +
         "}," +
         "{"text": "file 2.2"" +
         "}" +"]";
        writer.write(result.toString());
        writer.flush();
	}

	private void getPositon(HttpServletRequest request,
			HttpServletResponse response) throws IOException {
		PrintWriter writer =  response.getWriter();
        String result = 
        "["+
         "{"text": "研发"," +
             ""expanded": true," +
             ""children":" +
             "[" +
                 "{"+
                     ""text": "开发平台部"," +
                     ""children":" +
                     "[" +
                         "{"+
                             ""text": "部门经理"" +
                         "}," +
                         "{" +
                             ""text": "产品经理"" +
                         "}," +
                         "{"+
                         ""text": "开发工程师"" +
                         "}" +
                     "]" +
                 "}," +
                 "{" +
                     ""text": "基础平台部"," +
                     ""children":" +
                     "[" +
                         "{"+
                             ""text": "部门经理"" +
                         "}," +
                         "{" +
                             ""text": "产品经理"" +
                         "}," +
                         "{"+
                         ""text": "开发工程师"" +
                         "}" +
                     "]" +
                 "}," +
                 "{"+
                    ""text": "工具平台部"," +
                    ""children":" +
                    "[" +
                        "{"+
                            ""text": "部门经理"" +
                        "}," +
                        "{" +
                            ""text": "产品经理"" +
                        "}," +
                        "{"+
                        ""text": "开发工程师"" +
                        "}" +
                    "]" +
                 "}," +
                 "{" +
                     ""text": "测试部"," +
                     ""children":" +
                     "[" +
                         "{"+
                             ""text": "部门经理"" +
                         "}," +
                         "{" +
                             ""text": "测试人员"" +
                         "}" +
                     "]" +
                 "}" +
             "]" +
         "}," +
         "{" +
             ""text": "销售"," +
             ""expanded": true," +
             ""children":" +
             "[" +
                 "{"+
                     ""text": "销售总监"" +
                 "}," +
                 "{" +
                     ""text": "市场分析员"" +
                 "}," +
                 "{"+
                 ""text": "销售人员"" +
                 "}" +
             "]" +
         "}," +
         "{" +
             ""text": "人事"," +
             ""expanded": true," +
             ""children":" +
             "[" +
                 "{"+
                     ""text": "人力资源总监"" +
                 "}," +
                 "{" +
                     ""text": "薪酬管理员"" +
                 "}," +
                 "{"+
                 ""text": "招聘人员"" +
                 "}" +
             "]" +
         "}" +
     "]";
        writer.write(result.toString());
        writer.flush();
		
	}
    
}