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JSON學習筆記之一

首先，使用JavaScript的eval()函數實現，將JSON數據串轉換成為一個JavaScript對象數組。這里，在Servlet中訪問數據庫取得記錄，并合成JSON串，發送到客戶端。

一般，對于企業級應用，使用JavaScript的eval()函數，存在安全隱患問題。這個例子就是感受一下JSON數據串從服務器段被傳送到客戶端之后，將數據轉換成為對象數組或者對象，從而方便地使用JavaScript來實現遍歷。

看一下我的Permission實體的Hibernate映射文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "

<hibernate-mapping>
<class name="model.xgb.vo.Permission" table="PERMISSION" lazy="false">
    <composite-id>
      <key-property name="id" column="ID" type="integer"/>
      <key-property name="term" column="TERM" type="string"/>
    </composite-id>
    <property name="endDate" column="ENDDATE" type="date"/>
    <property name="start" column="START" type="date"/>
    <many-to-one name="roles" class="model.xgb.vo.Role" lazy="false" unique="true" cascade="save-update">
      <column name="ROLE_ID"/>
    </many-to-one>
    <many-to-one name="org" class="model.xgb.vo.Org" lazy="false" unique="true" cascade="save-update">
      <column name="ORG_ID"/>
    </many-to-one>
    <many-to-one name="operator" class="model.xgb.vo.Operator" lazy="false" unique="true" cascade="save-update">
      <column name="OPERATOR_ID"/>
      <column name="OPERATOR_NAME"/>
      <column name="OPERATOR_TYPE"/>
    </many-to-one>
</class>
</hibernate-mapping>

現在，就是在Servlet中讀取對應的記錄，然后構造JSON數據，實現的Servlet為GetPermissions，如下所示：

package org.shirdrn.servlet;

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

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

import model.xgb.bo.ManagerService;
import model.xgb.bo.impl.ManagerServiceImpl;
import model.xgb.vo.Permission;
import cn.edu.cust.levin.BusinessException;
import cn.edu.cust.levin.business.BusinessFactory;

/** author http://www.bt285.cn http://www.5a520.cn
*/

public class GetPermissions extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
static final long serialVersionUID = 1L;

public GetPermissions() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   doPost(request,response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   request.setCharacterEncoding("utf-8");
   response.setCharacterEncoding("utf-8");
   response.setHeader("Cache-Control", "no-cache");
   response.setContentType("text/json;charset=UTF-8");
   String semester = java.net.URLDecoder.decode(request.getParameter("semester"),"UTF-8");
   int orgId = Integer.parseInt(request.getParameter("orgId"));
   PrintWriter out = response.getWriter();
   try {
    ManagerService managerService = (ManagerService)BusinessFactory
     .getBusiness(ManagerServiceImpl.class);
    List permissionList = managerService.getPermissionByOrg(orgId, semester);
    String jsonString = "[";
    for(int i=0;i<permissionList.size();i++) {
     Permission permission = (Permission)permissionList.get(i);
     jsonString += "{";
     jsonString += "\"id\":" + permission.getId() +",";
     jsonString += "\"semester\":\"" + permission.getTerm() +"\",";
     jsonString += "\"startTime\":\"" + permission.getStart().toLocaleString() +"\",";
     jsonString += "\"endTime\":\"" + permission.getEndDate().toLocaleString() +"\",";
     jsonString += "\"orgId\":" + permission.getOrg().getId() +",";
     jsonString += "\"operatorId\":" + permission.getOperator().getId() +",";
     jsonString += "\"operatorName\":\"" + permission.getOperator().getName() +"\",";
     jsonString += "\"roleId\":" + permission.getRoles().getId();
     if(i != permissionList.size()-1) {
      jsonString += "},";
     }
     else {
      jsonString += "}]";
     }
    }
    out.print(jsonString);
    out.flush();
    out.close();
   } catch (BusinessException e) {
    e.printStackTrace();
   }
}
}