将数据库中的数据读出，写成csv文件存在本地

一：需求分析：将数据从数据库查出后封装到本地的csv文件中

二：开发实现

1.导入依赖：

    com.alibaba
    druid
    1.0.20

2.编写工具类：

import java.io.BufferedWriter;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.OutputStream;  
import java.io.OutputStreamWriter;  
import java.net.URLEncoder;  
import java.util.Iterator;  
import java.util.LinkedHashMap;  
import java.util.List;  
import java.util.Map;  

import javax.servlet.http.HttpServletResponse;

import com.alibaba.druid.util.StringUtils;  


public class CSVUtils {
	   /**
	    * 功能说明：获取UTF-8编码文本文件开头的BOM签名。
	    * BOM(Byte Order Mark)，是UTF编码方案里用于标识编码的标准标记。例：接收者收到以EF BB BF开头的字节流，就知道是UTF-8编码。
	    * @return UTF-8编码文本文件开头的BOM签名
	    */
	    public static String getBOM() {

	         byte b[] = {(byte)0xEF, (byte)0xBB, (byte)0xBF};
	         return new String(b);
	    }
	    
	  /** 
	   * 生成CVS文件
	   * @param exportData 
	   *       源数据List 
	   * @param map 
	   *       csv文件的列表头map 
	   * @param outPutPath 
	   *       文件路径 
	   * @param fileName 
	   *       文件名称 
	   * @return 
	   */  
	  @SuppressWarnings("rawtypes")  
	  public static File createCSVFile(List exportData, LinkedHashMap map, String outPutPath,  
	                   String fileName) {  
	    File csvFile = null;  
	    BufferedWriter csvFileOutputStream = null;  
	    try {  
	      File file = new File(outPutPath);  
	      if (!file.exists()) {  
	        file.mkdirs();  
	      }  
	      //定义文件名格式并创建  
	      csvFile =new File(outPutPath+fileName+".csv");
	      file.createNewFile();  
	      // UTF-8使正确读取分隔符","  
	      //如果生产文件乱码，windows下用gbk，linux用UTF-8
	      csvFileOutputStream = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(  
	        csvFile), "UTF-8"), 1024);  
	      
	      //写入前段字节流，防止乱码
	      csvFileOutputStream.write(getBOM());
	      // 写入文件头部
	      for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator.hasNext();) {  
	        java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator.next();  
	        csvFileOutputStream.write((String) propertyEntry.getValue() != null ? (String) propertyEntry.getValue() : "" );  
	        if (propertyIterator.hasNext()) {  
	          csvFileOutputStream.write(",");  
	        }  
	      }  
	      csvFileOutputStream.newLine();  
	      // 写入文件内容  
	      for (Iterator iterator = exportData.iterator(); iterator.hasNext();) {  
	          Object row = (Object) iterator.next();
	        for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator  
	          .hasNext();) {  
	          java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator  
	            .next();  
	          String str=row!=null?((String)((Map)row).get( propertyEntry.getKey())):"";

	          if(StringUtils.isEmpty(str)){
	              str="";
	          }else{
	              str=str.replaceAll("\"","\"\"");
	              if(str.indexOf(",")>=0){
	                  str="\""+str+"\"";
	              }
	          }
	          csvFileOutputStream.write(str);  
	          if (propertyIterator.hasNext()) {  
	            csvFileOutputStream.write(",");  
	          }  
	        }  
	        if (iterator.hasNext()) {  
	          csvFileOutputStream.newLine();  
	        }  
	      }  
	      csvFileOutputStream.flush();  
	    } catch (Exception e) {  
	      e.printStackTrace();  
	    } finally {  
	      try {  
	        csvFileOutputStream.close();  
	      } catch (IOException e) {  
	        e.printStackTrace();  
	      }  
	    }  
	    return csvFile;  
	  }  
	   
	  /**
	   *     生成并下载csv文件
	   * @param response
	   * @param exportData
	   * @param map
	   * @param outPutPath
	   * @param fileName
	   * @throws IOException
	   */
	  @SuppressWarnings("rawtypes")
	  public static void exportDataFile(HttpServletResponse response,List exportData, LinkedHashMap map, String outPutPath,String fileName) throws IOException{
	      File csvFile = null;  
	        BufferedWriter csvFileOutputStream = null;  
	        try {  
	          File file = new File(outPutPath);  
	          if (!file.exists()) {  
	            file.mkdirs();  
	          }  
	          //定义文件名格式并创建  
	          csvFile =new File(outPutPath+fileName+".csv");
	          if(csvFile.exists()){
	             csvFile.delete(); 
	          }
	          csvFile.createNewFile();  
	          // UTF-8使正确读取分隔符","  
	          //如果生产文件乱码，windows下用gbk，linux用UTF-8
	          csvFileOutputStream = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(csvFile), "UTF-8"), 1024);  
	          //写入前段字节流，防止乱码
	          csvFileOutputStream.write(getBOM());
	          // 写入文件头部  
	          for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator.hasNext();) {  
	            java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator.next();  
	            csvFileOutputStream.write((String) propertyEntry.getValue() != null ? (String) propertyEntry.getValue() : "" );  
	            if (propertyIterator.hasNext()) {  
	              csvFileOutputStream.write(",");  
	            }  
	          }  
	          csvFileOutputStream.newLine();  
	          // 写入文件内容  
	          for (Iterator iterator = exportData.iterator(); iterator.hasNext();) {  
	            Object row = (Object) iterator.next();  
	            for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator  
	              .hasNext();) {  
	              java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator  
	                .next();  
	              String str=row!=null?((String)((Map)row).get( propertyEntry.getKey())):"";
	              if(StringUtils.isEmpty(str)){
	                  str="";
	              }else{
	                  str=str.replaceAll("\"","\"\"");
	                  if(str.indexOf(",")>=0){
	                      str="\""+str+"\"";
	                  }
	              }
	              csvFileOutputStream.write(str);  
	              if (propertyIterator.hasNext()) {  
	                csvFileOutputStream.write(",");  
	              }  
	            }  
	            if (iterator.hasNext()) {  
	              csvFileOutputStream.newLine();  
	            }  
	          }  
	          csvFileOutputStream.flush();  
	        } catch (Exception e) {  
	          e.printStackTrace();  
	        } finally {  
	          try {  
	            csvFileOutputStream.close();  
	          } catch (IOException e) {  
	            e.printStackTrace();  
	          }  
	        }  
	        
	        
	       
	       
	        InputStream in = null;  
	        try {  
	          in = new FileInputStream(outPutPath+fileName+".csv");  
	          int len = 0;  
	          byte[] buffer = new byte[1024];  
	         
	          OutputStream out = response.getOutputStream(); 
	          response.reset(); 
	           
	          response.setContentType("application/csv;charset=UTF-8");  
	          response.setHeader("Content-Disposition","attachment; filename=" + URLEncoder.encode(fileName+".csv", "UTF-8"));  
	          response.setCharacterEncoding("UTF-8"); 
	          while ((len = in.read(buffer)) > 0) {  
	            out.write(new byte[] { (byte) 0xEF, (byte) 0xBB, (byte) 0xBF });  
	            out.write(buffer, 0, len);  
	          }
	          out.close();
	        } catch (FileNotFoundException e) {  
	        } finally {  
	          if (in != null) {  
	            try {  
	              in.close();  
	            } catch (Exception e) {  
	              throw new RuntimeException(e);  
	            }  
	          }  
	        }
	       
	  }
	  
	  /** 
	   * 删除该目录filePath下的所有文件 
	   * @param filePath 
	   *      文件目录路径 
	   */  
	  public static void deleteFiles(String filePath) {  
	    File file = new File(filePath);  
	    if (file.exists()) {  
	      File[] files = file.listFiles();  
	      for (int i = 0; i < files.length; i++) {  
	        if (files[i].isFile()) {  
	          files[i].delete();  
	        }  
	      }  
	    }  
	  }  
	   
	  /** 
	   * 删除单个文件 
	   * @param filePath 
	   *     文件目录路径 
	   * @param fileName 
	   *     文件名称 
	   */  
	  public static void deleteFile(String filePath, String fileName) {  
	    File file = new File(filePath);  
	    if (file.exists()) {  
	      File[] files = file.listFiles();  
	      for (int i = 0; i < files.length; i++) {  
	        if (files[i].isFile()) {  
	          if (files[i].getName().equals(fileName)) {  
	            files[i].delete();  
	            return;  
	          }  
	        }  
	      }  
	    }  
	  }  
	   
	    

}

3.编程Controller层

@RequestMapping(value = "/get")
		public Object getPerson(){
//			String sql = "select * from test008 where id=?";
			 String sql = "select * from event_type   ";
	           
		      List> queryForList2 = jdbc.queryForList(sql);
		      List

转换成json的方法

  List> queryForList2 = jdbc.queryForList(sql);
	      String str = JSON.toJSONString(queryForList2);