SpringBoot 实现通用导出excel文件案例

拼搏现实的明天。 2023-10-04 23:09 29阅读 0赞

**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**

<dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>3.15</version>
    </dependency>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-scratchpad</artifactId>
        <version>3.15</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.69</version>
    </dependency>
    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>2.5</version>
    </dependency>

**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<String, Object> 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<Map<String, Object>> 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<String, Object> 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 <T>
         * @return
         */
        public static<T> Map<String, Object> toMap(T entity){
            Class<? extends Object> bean = entity.getClass();
            Field[] fields = bean.getDeclaredFields();
            Map<String, Object> 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<District> 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 <T> List<String> resolveExcelTableName(T entity) {
        List<String> tableNamesList = new ArrayList<>();
        Class<? extends Object> bean = entity.getClass();
        Field[] fields = bean.getDeclaredFields();
        Map<String, Object> 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<String> 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<String> nameList = MapUtils.resolveExcelTableName(user);
        System.out.println(nameList.toString());
        String tableNames = buildCsvFileTableNamesNew(nameList);
        System.out.println(tableNames);
    
    }