扩展Struts2,傻瓜化将数据导出为excel

zhxp791008

以前做开发，在有数据导出为excel的时候，不加思索就一个cell一个cell地拼凑完成一个excel内存流，输入出到客户端了事，有天想这些代码80%都是重复的，能不能不那么麻烦地ctrl c、ctrl v来做这件事。尝试了下，还可以。（代码部份中是演示）
首先定义一个Annotation
@Retention(RetentionPolicy.RUNTIME)public @interface Excel {String title() default "";}
在需要导出为excel的类上加上此Excel注解，如：
class User {public User(String name, Integer age) {  this.name = name;  this.age = age;}private String name;private Integer age;@Excel(title = "姓名")public String getName() {  return name;}public void setName(String name) {  this.name = name;}@Excel(title = "年龄")public Integer getAge() {  return age;}public void setAge(Integer age) {  this.age = age;}}

现在相当于配置内容有了，只需写一个工具类，完成向excel数据格式的转换。
这有个简单实现：
public static void export(List list, OutputStream os) {  List<String> titles = new ArrayList<String>();  Hashtable<String, List> data = parseData(list, titles);  try {   builderExcel(data, titles, list.size(), os);  } catch (Exception e) {   e.printStackTrace();  }}private static void builderExcel(Hashtable<String, List> data,   List<String> titles, int len, OutputStream os) throws Exception {  WritableWorkbook workbook = Workbook.createWorkbook(os);  WritableSheet ws = workbook.createSheet("sheet1", 0);//  for (int i = 0; i < titles.size(); i++) {   Label labelC = new Label(i, 0, titles.get(i));   ws.setColumnView(i, 20);   ws.addCell(labelC);     }  for (int i = 0; i < len; i++) {   for (int j = 0; j < titles.size(); j++) {    List<Object> context = data.get(titles.get(j));    Object o = context.get(i);    WritableCell labelC = null;    if (o instanceof String) {     labelC = new Label(j, i + 1, o.toString());    }     else if(o instanceof Double)    {     labelC = new Number(j, i + 1, (Double)o);    }    else if(o instanceof Date)    {     labelC = new DateTime(j, i + 1, (Date)o);    }    ws.addCell(labelC);   }  }  workbook.write();  workbook.close();}private static Hashtable parseData(List list, List titles) {  Hashtable<String, List> data = new Hashtable<String, List>();  for (Object obj : list) {   Method[] methods = obj.getClass().getMethods();   for (Method m : methods) {    if (m.isAnnotationPresent(Excel.class)) {     Excel excel = m.getAnnotation(Excel.class);     String title = excel.title();     List<Object> cols = data.get(title);     if (cols == null) {      titles.add(title);      cols = new ArrayList<Object>();     }     try {      cols.add(m.invoke(obj));     } catch (IllegalArgumentException e) {      // TODO Auto-generated catch block      e.printStackTrace();     } catch (IllegalAccessException e) {      // TODO Auto-generated catch block      e.printStackTrace();     } catch (InvocationTargetException e) {      // TODO Auto-generated catch block      e.printStackTrace();     }     data.put(title, cols);    }   }  }  return data;}}

最后一步，扩展struts2的resulttype.public class ExcelResult extends StrutsResultSupport {     private String dataList = "dataList";     private String fileName = "fileName";     protected void doExecute(String arg0, ActionInvocation actionInvocation)      throws Exception { ActionContext ctx = actionInvocation.getInvocationContext(); HttpServletRequest request = (HttpServletRequest) ctx   .get(org.apache.struts2.StrutsStatics.HTTP_REQUEST); HttpServletResponse response = (HttpServletResponse) ctx   .get(org.apache.struts2.StrutsStatics.HTTP_RESPONSE); String excelfile = (String) request.getAttribute(fileName); setXlsHeader(response, excelfile); OutputStream os = response.getOutputStream(); List list = (List) request.getAttribute(dataList); ExcelExporter.export(list, os); os.close();     }     public void setDataList(String dataList) { this.dataList = dataList;     }     public void setFileName(String fileName) { this.fileName = fileName;     }     private void setXlsHeader(HttpServletResponse rs, String fn)      throws UnsupportedEncodingException { rs.setContentType("application/vnd.ms-excel"); String fileName = new String(fn.getBytes("GBK"), "ISO-8859-1"); rs.setHeader("Content-disposition", "attachment; filename=" + fileName);     } }
现在看看程序员需要做的事：
List<User> userList = userService.findAll();request.setAttribute("dataList",userList);
在struts2的配置文件中加入
<result name="success" type="excel">
</result>
当然你得在需要导出的类中加入Excel的注解和定义一下excel的resulttype.