java反射(二)-基于反射和注解的Excel解析工具Demo

基于反射和注解的Excel解析工具Demo

原理

反射的运用部分

通过Class的Field，可以给对应Class的Field字段对应的属性设值

注解的运用部分

通过给实体类的属性加上注解，和Excel中的表头做关联，就可以在解析Excel的时候，更加灵活

需要的poi的包

需要依赖的解析Excel的jar包有：
poi-3.10-FINAL.jar
poi-ooxml-3.10-FINAL.jar
poi-ooxml-schemas-3.10-FINAL.jar
xmlbeans-2.6.0.jar

代码实现

创建注解

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface CellMapping {

    String cellName() default "";

}

创建Excel文件

当然，需要注意的是，保存的时候，要存成.xls格式的，不要存.xlsx格式的。可能因为问题，解析不了。

对应的实体类:

public class Car {

    @CellMapping(cellName = "汽车品牌")
    public String name;

    @CellMapping(cellName = "汽车类型")
    public String type;

    @Override
    public String toString() {
        return "[name=" + name + ", type=" + type + "]";
    }
}

解析工具类：

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;

public class FastExcel {

    private Workbook workbook = null;
    private Sheet sheet = null;

    public FastExcel(String path) throws InvalidFormatException, IOException {
        File file = new File(path);
        workbook = WorkbookFactory.create(file);
        sheet = workbook.getSheetAt(0);
    }

    public FastExcel(InputStream is) throws InvalidFormatException, IOException {
        workbook = WorkbookFactory.create(is);
        sheet = workbook.getSheetAt(0);
    }

    public  List praseExcel(Class clazz) {
        List rst = new ArrayList<>();
        if (sheet == null)
            return rst;
        int firstRowNum = sheet.getFirstRowNum();
        Row row = sheet.getRow(firstRowNum);
        short lastCellNum = row.getLastCellNum();

        // key:表头,value:对应的列数
        Map cellNames = getCellMapping(row, lastCellNum);

        // key:映射的表头名字,value:对应的字段
        Map annotations = getFeildMapping(clazz);

        int lastRowNum = sheet.getLastRowNum();
        Set keys = cellNames.keySet();
        try {
            for (int rowIndex = (++firstRowNum); rowIndex <= lastRowNum; rowIndex++) {
                T inst = clazz.newInstance();
                Row r = sheet.getRow(rowIndex);
                for (String key : keys) {
                    Field field = annotations.get(key);
                    if (field == null)
                        continue;
                    Integer col = cellNames.get(key);
                    Cell cel = r.getCell(col);
                    if (cel == null)
                        continue;
                    field.setAccessible(true);
                    String val = cel.getStringCellValue();
                    field.set(inst, val);
                }
                rst.add(inst);
            }
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return rst;
    }

    /**
     * 获取表头和列的映射关系
     * 
     * @param row
     * @param lastCellNum
     * @return
     */
    private Map getCellMapping(Row row, short lastCellNum) {
        // key:表头,value:对应的列数
        Map cellNames = new HashMap<>();
        Cell cell;
        for (int col = 0; col < lastCellNum; col++) {
            cell = row.getCell(col);
            String val = cell.getStringCellValue();
            cellNames.put(val, col);
        }
        return cellNames;
    }

    /**
     * 获取对象字段和Excel表头的字段映射关联
     * 
     * @param clazz
     * @return
     */
    private  Map getFeildMapping(Class clazz) {
        // key:映射的表头名字,value:对应的字段
        Map annotations = new HashMap<>();
        Field[] fields = clazz.getDeclaredFields();
        if (fields == null || fields.length < 1)
            return annotations;
        for (Field field : fields) {
            CellMapping mapping = field.getAnnotation(CellMapping.class);
            if (mapping == null) {
                annotations.put(field.getName(), field);
            } else {
                annotations.put(mapping.cellName(), field);
            }
        }
        return annotations;
    }

}

运行结果：

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.poi.openxml4j.exceptions.InvalidFormatException;

public class CarTest {

    public static void main(String[] args) {
        try {
            InputStream is = CarTest.class.getResourceAsStream("汽车.xls");
            FastExcel fastExcel = new FastExcel(is);
            List rst = fastExcel.praseExcel(Car.class);
            for (Car car : rst) {
                System.out.println(car.toString());
            }
        } catch (InvalidFormatException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

结论：

最终解析结果为：
[name=宝马, type=轿跑]
[name=奔驰, type=suv]
[name=兰博基尼, type=超跑]
[name=特斯拉, type=电动轿跑]
[name=长安, type=面包车]

将实体类字段和Excel表头做绑定，可以不用再写非常多的硬转换代码，提高解析Excel的效率。而且易于维护。
当然，当前只是一个Demo，还没有做到各种数据类型的支持，比如double，时间等等类型的支持。
先记录一下，再优化