java 按顺序 列间用逗号隔开 逐行写入txt文件（使用反射、linkedHashMap实现有序输出）

主题：java生成txt文件。

这里有个需求：按顺序导出多列 列之间用逗号隔开。

有序输出到txt ‘有序’的实现方式：1、使用java反射按属性定义顺序读取字符串 2、使用linkedHashMap有序map来遍历键值对。

支持导出流以及直接输出到指定文件夹下。

具体代码如下：

package javacommon.file;import java.io.ByteArrayInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.UnsupportedEncodingException;import java.lang.reflect.Field;import java.util.LinkedHashMap;import java.util.List;import org.apache.commons.lang.StringUtils;public class TxtFileExceport {private static String fileName = null;private static final String defualtCharset = "GBK";private static final String newLine = "\r\n";/** * 传入类 、该类的结果集 、编码字符集 产生对应的流 * @param clazz * @param list * @param charset * @return */public static InputStream exportInputStreamFromClass(Class clazz, List<?> list,String charset) {String content = getExportStringFromClass(clazz, list);return getInputStream(content, charset);}/** * 传入类、类的集合、编码字符集、导出路径 自动生成文件到指定路径 * @param clazz * @param list * @param charset * @param exportUrl */public static void exportFileFromClass(Class clazz, List<?> list, String charset,String exportUrl) {String content = getExportStringFromClass(clazz, list);export(content, charset, exportUrl);}/** * 传入linkedhashmap，编码字符集 产生对应的流文件 * @param list * @param charset * @return */public static InputStream exportInputStreamFromMap(List<LinkedHashMap<Object, Object>> list,String charset) {String content = getExportStringFromMap(list);return getInputStream(content, charset);}/** * 传入linkedhashmap、编码字符集、导出路径 自动生成文件到指定路径 * @param list * @param charset * @param exportUrl */public static void exportFileFromMap(List<LinkedHashMap<Object, Object>> list, String charset,String exportUrl) {String content = getExportStringFromMap(list);export(content, charset, exportUrl);}public static void export(String content, String charset, String exportUrl) {FileOutputStream out = null;try {out = new FileOutputStream(exportUrl);InputStream io = getInputStream(content, charset);int length = 1024;byte[] buffer = new byte[1024];while ((length = io.read(buffer)) > -1) {out.write(buffer, 0, length);}out.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static void main(String[] args) {/*List<TxtDemo> txtDemos = TxtDemo.generator();//getExportString(TxtDemo.class,txtDemos);TxtFileExceport.fileName = "billDownload"+new Date().getTime();String urlString = "D:/tmp/billDownload/" + fileName + ".txt";exportFile(TxtDemo.class, txtDemos, null, urlString); List<LinkedHashMap<Object, Object>> lists=TxtDemo.generatorMap(); export(getExportStringFromMap(lists), null, urlString);*/}/** * 反射拼接类的属性值 * @param clazz * @param list * @return */public static String getExportStringFromClass(Class clazz, List<?> list) {StringBuffer sb = new StringBuffer();for (Object object : list) {Field[] fs = clazz.getDeclaredFields();for (int i = 0; i < fs.length; i++) {Field field = fs[i];field.setAccessible(true);String valString;try {valString = field.get(object).toString();if (i == (fs.length - 1)) {sb.append(valString + newLine);} else {sb.append(valString + ",");}} catch (IllegalArgumentException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IllegalAccessException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}return sb.toString();}/**遍历 拼接value值 * @param list * @return */public static String getExportStringFromMap(List<LinkedHashMap<Object,Object>> list) {StringBuffer sb = new StringBuffer();for(int i=0;i<list.size();i++){LinkedHashMap<Object,Object> linkMap=list.get(i);int index=0;for(Object obj:linkMap.values()){if(obj==null){if(index==linkMap.values().size()-1){sb.append(""+newLine);}else{sb.append(",");}}else{if(index==linkMap.values().size()-1){sb.append(obj.toString()+newLine);}else{sb.append(obj.toString()+",");}}index++;}}return sb.toString();}public static InputStream getInputStream(String string, String charset) {byte[] bytes = null;try {if (StringUtils.isEmpty(charset)) {bytes = string.getBytes(defualtCharset);} else {bytes = string.getBytes(charset);}} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();}return new ByteArrayInputStream(bytes);}public String getFileName() {return fileName;}public void setFileName(String fileName) {this.fileName = fileName;}}