首先是通過方法把對應的文檔編譯成為對應的pdf文件，然後再瀏覽器打開對應的pdf文件。從而實現預覽效果；

但要註意的是，預覽打開的url存在中文問題，我這邊始終存在因為轉義，而提示無法找到對應的pdf文件的問題。最後是再文檔編譯的時候使用文檔再數據庫對應的ID作為pdf名稱編譯出來，然後打開。

一下是後臺對應的代碼；

這裏提供兩張編譯方式，我所使用的是編譯成pdf文件。另一種是編譯成html文件。

要註意的是，需要再WEB-INF下面加上classes包，內容在附件中(這些內容必不可少；是代碼在編譯時用到的配置文件)；

package ths.project.EnterService.util.attachments.web;

import java.io.File;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import org.aspectj.weaver.patterns.HasMemberTypePattern;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import com.google.gson.JsonArray;
import com.sun.org.apache.bcel.internal.generic.NEW;

import ths.jdp.core.dao.base.Paging;
import ths.jdp.core.model.FormModel;
import ths.jdp.project.web.LoginCache;
import ths.project.EnterService.user.service.UserAccountRelationService;
import ths.project.EnterService.util.attachments.service.AttachmentsService;
import ths.project.EnterService.util.toPdf.Excel2Pdf;
import ths.project.EnterService.util.toPdf.PowerPoint2Pdf;
import ths.project.EnterService.util.toPdf.WordToPdf;

/**
 * 附件在線預覽
 * 
 * @author xwy
 * @since 2019-3-8
 */
@Controller
@RequestMapping("/attachments")
public class AttachmentsController {

	@Autowired
	private AttachmentsService attachmentsService;
	

	/**
	 * 在線預覽 查詢表單對應的附件信息
	 * @param fileName
	 * forcePreview 強制轉換
	 */
	@RequestMapping("/file")
	public ModelAndView file(@RequestParam String ext,String business_key,Paging<Map<String, Object>> pageInfo, HttpServletRequest request){
		ModelAndView result = new ModelAndView("attachments/file");
		Map<String,Object> map=new HashMap<String,Object>();
		Paging<Map<String, Object>> dateMap = new Paging<Map<String, Object>>();
		map.put("BUSINESS_KEY", business_key);
		map.put("EXT", ext);
		dateMap=attachmentsService.getBusinesskey(pageInfo,map);
		result.addObject("pageInfo",dateMap);
        return result;
	}
	
	/**
	 * 在線預覽
	 * @param fileName
	 * forcePreview 強制轉
	 */
	@RequestMapping("/previewToPdf")
	public ModelAndView previewToPdf(@RequestParam String fileid,String forcePreview,HttpServletRequest request){
		ModelAndView result = new ModelAndView("attachments/showPdf");
		Map<String,Object> map=new HashMap<String,Object>();
		map.put("FILE_ID", fileid);
		map=attachmentsService.getFileid(map);
		String path=(String)map.get("FILE_NAME");
		String name=(String)map.get("FILE_PATH");
//		
		String filePath=request.getRealPath("attachments")+"\\"+path;//獲取文件絕對路徑
		File f = new File(request.getRealPath("attachments")+"\\"+fileid+".pdf");//判斷文件是否已經生成
        boolean hasToPDF = f.exists();
//        result.addObject("path",ajaxToChinse(path.substring(0,path.lastIndexOf("."))+".pdf"));//展示路徑 name+"\\"+
        result.addObject("fileid",fileid);
		if("force".equals(forcePreview)||!hasToPDF){//查看是否已經存在編譯好的；如果是強制轉換 則轉換,或者沒有轉換*/
			 try{
			    ToPdf( filePath,filePath,request.getRealPath("attachments")+"\\"+fileid+".pdf");
//這裏進行編譯對應的文檔
			}catch(Exception e){
				result.addObject("path","");//清空路徑
				result.addObject("error", "異常："+e.getMessage());
			} 
		}
			result.addObject("path",fileid+".pdf");
        return result;
	}
	/**
	 * 文件轉換 方便實現在線預覽
	 * @param filePath
	 * @param path
	 */
	public void ToPdf(String filePath,String path,String paths) throws Exception{
		System.out.println("開始文件類型轉換,文件原始路徑："+filePath);
		String fileExt = path.substring(path.lastIndexOf(".") + 1).toLowerCase();//文件後綴
		if("doc".equals(fileExt) || "docx".equals(fileExt)){
			WordToPdf.wordToOther(filePath,"pdf",paths);
		} else if("xls".equals(fileExt) || "xlsx".equals(fileExt)){
			Excel2Pdf.convertFile(filePath, "pdf");
		} else if("ppt".equals(fileExt) || "pptx".equals(fileExt)){
			PowerPoint2Pdf.convertFile(filePath, "pdf");
		}else{
			throw new Exception("不支持在線預覽");
		}
	}
	
	//ajax 中文傳參之後解碼
			public String ajaxToChinse(String code){
				String val1 = null;
		    	String val2 = null;
				if(code!=null && !("").equals(code)){
					try {
						val1= URLDecoder.decode(code, "UTF-8");
						val2= URLDecoder.decode(val1, "UTF-8");
					} catch (UnsupportedEncodingException e) {
						e.printStackTrace();
					}
				}
				return val2;
			}
}

記錄一下，實現各種文檔在線預覽的功能