SpringBoot 实现通用导出excel文件案例
核心的思路：
① 从不确定的类的集合list 中，取出里面的类，采用反射技术，取出类的属性名， 做第一行表格行标题名称拼接。
②拼接内容，由于类不确定，则采取反射把类全部字段属性作为key映射至map，同时把值放入value，最后，拼接内容的时候只需要map进行数据拼接即可。
1.依赖
org.apache.poi
poi-ooxml
3.15
org.apache.poi
poi-scratchpad
3.15
com.alibaba
fastjson
1.2.69
commons-io
commons-io
2.5
2. 核心的工具类：CsvFileUtil.java
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.IOUtils;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.*;
/**
* @author splendor.s
* @date 2023/03/09 14:12 周日
*/
@Slf4j
public class CsvFileUtil {
public static final String FILE_SUFFIX = ".csv";
public static final String CSV_DELIMITER = ",";
public static final String CSV_TAIL = "\r\n";
protected static final String DATE_STR_FILE_NAME = "yyyyMMddHHmmssSSS";
/**
* 将字符串转成csv文件
*/
public static void createCsvFile(String savePath, String contextStr) throws IOException {
File file = new File(savePath);
//创建文件
file.createNewFile();
//创建文件输出流
FileOutputStream fileOutputStream = new FileOutputStream(file);
//将指定字节写入此文件输出流
fileOutputStream.write(contextStr.getBytes("gbk"));
fileOutputStream.flush();
fileOutputStream.close();
}
/**
* 写文件
*
* @param fileName
* @param content
*/
public static void writeFile(String fileName, String content) {
FileOutputStream fos = null;
OutputStreamWriter writer = null;
try {
fos = new FileOutputStream(fileName, true);
writer = new OutputStreamWriter(fos, "GBK");
writer.write(content);
writer.flush();
} catch (Exception e) {
log.error("写文件异常|{}", e);
} finally {
if (fos != null) {
IOUtils.closeQuietly(fos);
}
if (writer != null) {
IOUtils.closeQuietly(writer);
}
}
}
/**
* 构建文件名称
* @param dataList
* @return
*/
public static String buildCsvFileFileName(List dataList) {
return dataList.get(0).getClass().getSimpleName() + new SimpleDateFormat(DATE_STR_FILE_NAME).format(new Date()) + FILE_SUFFIX;
}
/**
* 构建excel 标题行名
* @param dataList
* @return
*/
public static String buildCsvFileTableNames(List dataList) {
Map map = toMap(dataList.get(0));
StringBuilder tableNames = new StringBuilder();
for (String key : map.keySet()) {
tableNames.append(key).append(MyCsvFileUtil.CSV_DELIMITER);
}
return tableNames.append(MyCsvFileUtil.CSV_TAIL).toString();
}
/**
* 构建excel内容
* @param dataLists
* @return
*/
public static String buildCsvFileBodyMap(List dataLists) {
//通过反射转成Map
List> mapList = new ArrayList<>();
for (Object o : dataLists) {
mapList.add(toMap(o));
}
//然后利用csv格式，遍历map并拼接数据
StringBuilder lineBuilder = new StringBuilder();
for (Map rowData : mapList) {
for (String key : rowData.keySet()) {
Object value = rowData.get(key);
if (Objects.nonNull(value)) {
lineBuilder.append(value).append(CsvFileUtil.CSV_DELIMITER);
} else {
lineBuilder.append("--").append(CsvFileUtil.CSV_DELIMITER);
}
}
lineBuilder.append(CsvFileUtil.CSV_TAIL);
}
return lineBuilder.toString();
}
/**
* 类转map
* @param entity
* @param
* @return
*/
public static Map toMap(T entity){
Class bean = entity.getClass();
Field[] fields = bean.getDeclaredFields();
Map map = new HashMap<>(fields.length);
for(Field field:fields){
try {
if(!"serialVersionUID".equals(field.getName())){
String methodName = "get"+field.getName().substring(0, 1).toUpperCase()+field.getName().substring(1);
Method method = bean.getDeclaredMethod(methodName);
Object fieldValue = method.invoke(entity);
map.put(field.getName(),fieldValue);
}
} catch (Exception e) {
log.warn("toMap() Exception={}",e.getMessage());
}
}
return map;
}
} 测试代码：
@RequestMapping("/createCsvFileJcTest")
public void createCsvFileJcTest() {
//类不确定 随便怎么传都行
List districts = districtService.queryByParentCodes(Arrays.asList("110100"));
//存放地址&文件名
String fileName = "D:\\mycsv\\"+CsvFileUtil.buildCsvFileFileName(districts);
//创建表格行标题
String tableNames = CsvFileUtil.buildCsvFileTableNames(districts);
//创建文件
CsvFileUtil.writeFile(fileName, tableNames);
//写入数据
String contentBody = CsvFileUtil.buildCsvFileBodyMap(districts);
//调用方法生成
CsvFileUtil.writeFile(fileName, contentBody);
} 扩展：
文件中导出的表头是属性名，如果正式的导出通常需要自定义表头名称，这里可以使用自定义注解来处理。
JcExcelName.java
@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface JcExcelName {
String name() default "";
}然后在想导出的类的属性上加上@JcExcelName，否则会默认取属性名做表格头：
例如：@JcExcelName(name="用户名称")
增加一个新的反射解析拿字段属性注解值函数：
public static List resolveExcelTableName(T entity) {
List tableNamesList = new ArrayList<>();
Class bean = entity.getClass();
Field[] fields = bean.getDeclaredFields();
Map map = new HashMap<>(fields.length);
for (Field field : fields) {
try {
if (!"serialVersionUID".equals(field.getName())) {
String tableTitleName = field.getName();
JcExcelName myFieldAnn = field.getAnnotation(JcExcelName.class);
String annName = myFieldAnn.name();
if (StringUtils.hasLength(annName)) {
tableTitleName = annName;
}
tableNamesList.add(tableTitleName);
}
} catch (Exception e) {
log.warn("toMap() Exception={}", e.getMessage());
}
}
return tableNamesList;
} 然后根据解析出来的注解值列名拼接 表格标题名格式：
public static String buildCsvFileTableNamesNew(List dataList) {
StringBuilder tableNames = new StringBuilder();
for (String name : dataList) {
tableNames.append(name).append(MyCsvFileUtil.CSV_DELIMITER);
}
return tableNames.append(MyCsvFileUtil.CSV_TAIL).toString();
} 测试案例：
public static void main(String[] args) {
User user = new User();
List nameList = MapUtils.resolveExcelTableName(user);
System.out.println(nameList.toString());
String tableNames = buildCsvFileTableNamesNew(nameList);
System.out.println(tableNames);
}