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Simple Reading

This chapter introduces how to use FastExcel to perform simple Excel reading operations.

Data Listeners​

Overview​

FastExcel provides a listener mechanism for processing each row of data while reading Excel files.

Usage​

Data listeners need to be instantiated and support various usage patterns.

Instantiation​

Listeners cannot be managed by Spring and must be re-instantiated each time an Excel file is read.

Lambda Expressions​

@Test
public void simpleRead() {
    String fileName = "path/to/demo.xlsx";

    FastExcel.read(fileName, DemoData.class, new PageReadListener<>(dataList -> {
        for (DemoData demoData : dataList) {
            log.info("Read one record: {}", JSON.toJSONString(demoData));
        }
    })).sheet().doRead();
}

Anonymous Inner Classes​

@Test
public void simpleRead() {
    String fileName = "path/to/demo.xlsx";

    FastExcel.read(fileName, DemoData.class, new ReadListener<DemoData>() {
        @Override
        public void invoke(DemoData data, AnalysisContext context) {
           log.info("Read one record: {}", JSON.toJSONString(data));
        }

        @Override
        public void doAfterAllAnalysed(AnalysisContext context) {
            log.info("All data reading completed!");
        }
    }).sheet().doRead();
}

Data Listeners​

@Test
public void simpleRead() {
    String fileName = "path/to/demo.xlsx";

    FastExcel.read(fileName, DemoData.class, new DemoDataListener())
            .sheet()
            .doRead();
}

POJO Classes and Listeners​

Overview​

FastExcel provides a simple way to read Excel files. Users only need to define a POJO class to represent the data structure, then read data through FastExcel's listener mechanism.

POJO Class​

The DemoData POJO class corresponding to the Excel structure:

@Getter
@Setter
@EqualsAndHashCode
public class DemoData {
    private String string;
    private Date date;
    private Double doubleData;
}

Data Listener​

DemoDataListener is a custom listener used to process data read from Excel.

@Slf4j
public class DemoDataListener implements ReadListener<DemoData> {

    @Override
    public void invoke(DemoData data, AnalysisContext context) {
        log.info("Read one record: {}", JSON.toJSONString(data));
    }

    @Override
    public void doAfterAllAnalysed(AnalysisContext context) {
        log.info("All data reading completed!");
    }
}

Code Example​

@Test
public void simpleRead() {
    String fileName = "path/to/demo.xlsx";

    FastExcel.read(fileName, DemoData.class, new DemoDataListener())
            .sheet()
            .doRead();
}

Without POJO Classes and Listeners​

Overview​

FastExcel supports reading Excel files directly without defining POJO classes, using Map<Integer, String> to read data directly, where the key is the column index and the value is the cell data.

Data Listener​

@Slf4j
public class NoModelDataListener extends AnalysisEventListener<Map<Integer, String>> {

    @Override
    public void invoke(Map<Integer, String> data, AnalysisContext context) {
        log.info("Read one record: {}", JSON.toJSONString(data));
    }

    @Override
    public void doAfterAllAnalysed(AnalysisContext context) {
        log.info("All data reading completed!");
    }
}

Synchronous Reading​

Overview​

Use the doReadSync method to directly read Excel data into a list in memory. This method is recommended for scenarios with small data volumes. The read data can be either a list of POJO objects or a list of Maps.

POJO Class​

The DemoData POJO class corresponding to the Excel structure:

@Getter
@Setter
@EqualsAndHashCode
public class DemoData {
    private String string;
    private Date date;
    private Double doubleData;
}

Code Examples​

Reading as POJO Object List​

@Test
public void synchronousReadToObjectList() {
    String fileName = "path/to/demo.xlsx";

    // POJO Object List
    List<DemoData> list = FastExcel.read(fileName)
            .head(DemoData.class)
            .sheet()
            .doReadSync();

    for (DemoData data : list) {
        log.info("Read data: {}", JSON.toJSONString(data));
    }
}

Reading as Map List​

When not using POJOs, each row can be read as a Map, where the key is the column index and the value is the cell content.

@Test
public void synchronousReadToMapList() {
    String fileName = "path/to/demo.xlsx";

    // Map List
    List<Map<Integer, String>> list = FastExcel.read(fileName)
            .sheet()
            .doReadSync();

    for (Map<Integer, String> data : list) {
        log.info("Read data: {}", JSON.toJSONString(data));
    }
}