使用Spock编写Java函数单元测试时遭遇org.apache.poi.EmptyFileException

问题重现 #

测试用例（Spock）：

def "should generate claims error file"(){
    given:
    def tempFile = new TempFile()
    def excelErrorRecord = new ExcelErrorRecord(row: 5, col: 4, message: "Test Message")
    HashMap<String, List<ExcelErrorRecord>> errorRecords = new HashMap<>();
    errorRecords.put("Medical",[excelErrorRecord])
    def fileInputStream = Mock(FileInputStream)
    def workBook = Mock(Workbook)
    def file = Mock(File)

    and:
    tempFile.getFile() >> file
    file.length() >> 100
    tempFile.getFile().getAbsolutePath() >> "Temp File.xlsx"
    new FileInputStream(tempFile.getFile().getAbsolutePath()) >> fileInputStream
    new XSSFWorkbook(fileInputStream) >> workBook

    when:
    service.generateClaimsErrorFile(errorRecords, tempFile)

    then:
    noExceptionThrown()
}

被测Java代码片段：

try (FileInputStream fis = new FileInputStream(tempFile.getFile().getAbsolutePath());
     Workbook workbook = new XSSFWorkbook(fis)) 
{}
catch(Exception e){}

原因分析 #

抛出EmptyFileException的核心原因是：你Mock的FileInputStream对象没有任何可读的有效数据。XSSFWorkbook初始化时会尝试读取流内容，验证是否符合XLSX文件结构，当检测到流为空或无有效文件头时，就会抛出该异常。

测试中通过Spock构造方法Mock，让new FileInputStream(...)返回一个Mock实例，但这个Mock流未配置任何可读数据，POI库无法识别为有效Excel文件流，因此报错。

修复方案 #

有两种可行修复思路，可根据代码架构选择：

方案1：提供有效的Excel文件流 #

直接构造包含空XLSX文件内容的流，替换Mock的FileInputStream，让POI库能正常初始化Workbook：

def "should generate claims error file"(){
    given:
    def tempFile = new TempFile()
    def excelErrorRecord = new ExcelErrorRecord(row: 5, col: 4, message: "Test Message")
    HashMap<String, List<ExcelErrorRecord>> errorRecords = new HashMap<>();
    errorRecords.put("Medical",[excelErrorRecord])
    def workBook = Mock(Workbook)
    def file = Mock(File)

    // 构造包含空XLSX内容的字节流
    def tempXlsxOutput = new ByteArrayOutputStream()
    new XSSFWorkbook().write(tempXlsxOutput)
    def validInputStream = new ByteArrayInputStream(tempXlsxOutput.toByteArray())

    and:
    tempFile.getFile() >> file
    file.length() >> 100
    tempFile.getFile().getAbsolutePath() >> "Temp File.xlsx"
    // 让FileInputStream返回有效流
    new FileInputStream(_) >> validInputStream
    new XSSFWorkbook(_) >> workBook

    when:
    service.generateClaimsErrorFile(errorRecords, tempFile)

    then:
    noExceptionThrown()
}

方案2：重构代码，依赖注入Workbook创建逻辑 #

把Workbook的创建逻辑封装成独立依赖，通过构造方法注入到service中，测试时直接Mock该依赖，完全避开流处理：

第一步：重构Java代码

// 定义Workbook工厂接口
public interface WorkbookFactory {
    Workbook create(File file) throws IOException;
}

// 实现XSSF版本的工厂
public class XSSFWorkbookFactory implements WorkbookFactory {
    @Override
    public Workbook create(File file) throws IOException {
        try (FileInputStream fis = new FileInputStream(file.getAbsolutePath())) {
            return new XSSFWorkbook(fis);
        }
    }
}

// 修改Service类，注入工厂
public class ClaimsService {
    private final WorkbookFactory workbookFactory;

    // 构造方法注入
    public ClaimsService(WorkbookFactory workbookFactory) {
        this.workbookFactory = workbookFactory;
    }

    public void generateClaimsErrorFile(Map<String, List<ExcelErrorRecord>> errorRecords, TempFile tempFile) {
        try {
            // 使用工厂创建Workbook
            Workbook workbook = workbookFactory.create(tempFile.getFile());
            // 后续业务逻辑...
        } catch (IOException e) {
            // 异常处理...
        }
    }
}

第二步：修改Spock测试用例

def "should generate claims error file"(){
    given:
    def tempFile = new TempFile()
    def excelErrorRecord = new ExcelErrorRecord(row: 5, col: 4, message: "Test Message")
    HashMap<String, List<ExcelErrorRecord>> errorRecords = new HashMap<>();
    errorRecords.put("Medical",[excelErrorRecord])
    def workBook = Mock(Workbook)
    def file = Mock(File)
    // Mock工厂对象
    def workbookFactory = Mock(WorkbookFactory)
    // 初始化service时注入Mock的工厂
    def service = new ClaimsService(workbookFactory)

    and:
    tempFile.getFile() >> file
    workbookFactory.create(file) >> workBook

    when:
    service.generateClaimsErrorFile(errorRecords, tempFile)

    then:
    noExceptionThrown()
}

内容的提问来源于stack exchange，提问作者Thiluxan