Opencsv將csv文件轉(zhuǎn)成Bean

Maven依賴

    <dependency>
      <groupId>com.opencsv</groupId>
      <artifactId>opencsv</artifactId>
      <version>5.2</version>
    </dependency>

CsvToBeanBuilder

優(yōu)雅的解析文檔中的字段。將CSV文件轉(zhuǎn)換為Bean對象。

opencsv提供了基于"策略"的映射，將CSV綁定到bean。


16013479-954cb1d0f5887cab.png
接口名 策略
MappingStrategy 頂級的映射接口
headerColumnNameMappingStrategy 基于列名的映射策略，讀取csv文件的第一行作為header，比如header1，header2，header3然后調(diào)用bean的setHeader1方法，setHeader2方法，setHeader3方法分別設(shè)置值。**所以這種策略要求，列名與bean中的屬性名完全一致，如果不一致，則值為空，不會出錯。使用注解時，注解名字必須與csv中列名一致。
ColumnPositionMappingStrategy 列位置映射策略，他沒有header的概念，所以會輸出取所有行。在columnMapping數(shù)組中指定bean的屬性，第一個值對應(yīng)csv的第一列，第二個值對應(yīng)csv的第二列……
HeaderColumnNameTranslateMappingStrategy 列頭名字翻譯映射策略,與HeaderColumnNameMappintStrategy相比，bean的屬性名可以與csv列頭不一樣。通過指定map來映射。

注：bean的類型只能為基本數(shù)據(jù)類型以及String類型，若是BigDecimal類型，那么將會拋出異常。

Bean

@Data
@AllArgsConstructor
@NoArgsConstructor
public class CsvBean {
    //@CsvBindByName(column = "PLEG_FLTNO")
    @CsvBindByPosition(position = 0)
    private String PLEG_FLTNO;

    //@CsvBindByName(column = "PLEG_AP_THR_DEP")
    @CsvBindByPosition(position = 1)
    private String PLEG_AP_THR_DEP;

    //@CsvBindByName(column = "PLEG_AP_THR_ARR")
    @CsvBindByPosition(position = 2)
    private String PLEG_AP_THR_ARR;

    //@CsvBindByName(column = "PLEG_DATE")
    @CsvBindByPosition(position = 3)
    private String PLEG_DATE;

    //@CsvBindByName(column = "PLEG_LON")
    @CsvBindByPosition(position = 4)
    private String PLEG_LON;
}

csv文件：

"PLEG_FLTNO","PLEG_AP_THR_DEP","PLEG_AP_THR_ARR","PLEG_DATE","PLEG_LON","PLEG_LAT","PLEG_ALT","PLEG_SPE","PLEG_DIR","PLEG_TM_SEN","PLEG_UPDATE_TIME"
CA1658,SHE,PEK,"2019-12-01","122.388744","41.6808833","7193.28","618.966","278.53","2019-12-01 15:52:11","2019-12-01 15:54:15"
CA1658,SHE,PEK,"2019-12-01","122.255966","41.695625","7193.28","613.44","278.44","2019-12-01 15:53:14","2019-12-01 15:55:10"
CA1658,SHE,PEK,"2019-12-01","122.128377","41.7096805","7193.28","608.292","277.65","2019-12-01 15:54:16","2019-12-01 15:55:30"
CA1658,SHE,PEK,"2019-12-01","121.994802","41.7067388","7193.28","596.826","266.89","2019-12-01 15:55:21","2019-12-01 15:57:15"

基于列索引的映射

通俗點就是列位置映射，csv文件中列位置對應(yīng)到bean中的列。
需要注意的是，該策略會輸出所有的行，故，我們需要跳過某些行。

    @Test
    public void readCsvByPosition() throws Exception
    {
        String fileName="C:\\Users\\lyh\\Desktop\\CA1658SHE-PEK.csv";
        InputStreamReader is = new InputStreamReader(new  FileInputStream(fileName), StandardCharsets.UTF_8);
        ColumnPositionMappingStrategy<CsvBean> mappingStrategy = new ColumnPositionMappingStrategy<>();
        mappingStrategy.setType(CsvBean.class);
        CsvToBean<CsvBean> build = new CsvToBeanBuilder<CsvBean>(is)
                .withMappingStrategy(mappingStrategy)
                .withSeparator(CSVWriter.DEFAULT_SEPARATOR)
                .withSkipLines(1)   //跳過第一行
                .build();
        List<CsvBean> personList = build.parse();
        personList.forEach(System.out::println);
    }

結(jié)果

CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.388744)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.255966)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.128377)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=121.994802)

基于列名的映射

    @Test
    public void readCsvByName() throws Exception
    {
        String fileName="C:\\Users\\lyh\\Desktop\\CA1658SHE-PEK.csv";
        InputStreamReader is = new InputStreamReader(getInputStream(new  FileInputStream(fileName)), StandardCharsets.UTF_8);
        HeaderColumnNameMappingStrategy<CsvBean> mappingStrategy = new HeaderColumnNameMappingStrategy<>();
        mappingStrategy.setType(CsvBean.class);
        CsvToBean<CsvBean> build = new CsvToBeanBuilder<CsvBean>(is)
                .withMappingStrategy(mappingStrategy)
                .withSeparator(CSVWriter.DEFAULT_SEPARATOR)
                .build();
        List<CsvBean> personList = build.parse();
        personList.forEach(System.out::println);
    }

    /**
     * 讀取流中前面的字符，看是否有bom，如果有bom，將bom頭先讀掉丟棄
     *  (opencsv 按列名獲取bean對象，第一列缺失的情況)
     */
    public static InputStream getInputStream(InputStream in) throws IOException {

        PushbackInputStream testin = new PushbackInputStream(in);
        int ch = testin.read();
        if (ch != 0xEF) {
            testin.unread(ch);
        } else if ((ch = testin.read()) != 0xBB) {
            testin.unread(ch);
            testin.unread(0xef);
        } else if (testin.read() != 0xBF) {
            throw new IOException("錯誤的UTF-8格式文件");
        }
        return testin;
    }

結(jié)果

CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.388744)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.255966)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=122.128377)
CsvBean(PLEG_FLTNO=CA1658, PLEG_AP_THR_DEP=SHE, PLEG_AP_THR_ARR=PEK, PLEG_DATE=2019-12-01, PLEG_LON=121.994802)

轉(zhuǎn)換器

在csv獲取的都是字符串，這種情況下應(yīng)該使用轉(zhuǎn)換器。將csv中的字段轉(zhuǎn)換為對應(yīng)的bean中的字段類型。

@Data
@AllArgsConstructor
@NoArgsConstructor
public class CsvBean {
    //@CsvBindByName(column = "PLEG_FLTNO")
    @CsvBindByPosition(position = 0)
    private String PLEG_FLTNO;

    //@CsvBindByName(column = "PLEG_AP_THR_DEP")
    @CsvBindByPosition(position = 1)
    private String PLEG_AP_THR_DEP;

    //@CsvBindByName(column = "PLEG_AP_THR_ARR")
    @CsvBindByPosition(position = 2)
    private String PLEG_AP_THR_ARR;

    //@CsvBindByName(column = "PLEG_DATE")
    //@CsvBindByPosition(position = 3)
    @CsvCustomBindByPosition(position = 3,converter = ConvertToDate.class)
    private LocalDate PLEG_DATE;

    //@CsvBindByName(column = "PLEG_LON")
    @CsvBindByPosition(position = 4)
    private String PLEG_LON;
}

public class ConvertToDate extends AbstractBeanField {
    @Override
    protected Object convert(String s) throws CsvDataTypeMismatchException, CsvConstraintViolationException {
        return LocalDate.parse(s, DateTimeFormatter.ofPattern("yyyy-MM-dd"));
    }
}

注：若是列映射策略，則要使用@CsvCustomBindByPosition()注解。
注：若是名字映射策略，則要使用@CsvCustomBindByName()注解。

過濾器

opencsv提供了過濾器，可以過濾某些行，比如page header、page footer等

所有的過濾器必須實現(xiàn)CsvToBeanFilter 接口

public class CsvFilter implements CsvToBeanFilter {
    @Override
    public boolean allowLine(String[] strings) {
        return strings[4].equalsIgnoreCase("122.388744");
    }
}

CsvToBeanFilter 是一個函數(shù)式接口所以也可以直接簡化為lambda表達式

    @Test
    public void readCsvByPosition() throws Exception
    {
        String fileName="C:\\Users\\lyh\\Desktop\\CA1658SHE-PEK.csv";
        InputStreamReader is = new InputStreamReader(new  FileInputStream(fileName), StandardCharsets.UTF_8);
        ColumnPositionMappingStrategy<CsvBean> mappingStrategy = new ColumnPositionMappingStrategy<>();
        mappingStrategy.setType(CsvBean.class);
        CsvToBean<CsvBean> build = new CsvToBeanBuilder<CsvBean>(is)
                .withMappingStrategy(mappingStrategy)
                .withSeparator(CSVWriter.DEFAULT_SEPARATOR)
                .withSkipLines(1)
                .withFilter(param-> param[4].equalsIgnoreCase("122.388744"))  //增加過濾器
                //.withFilter(new CsvFilter())
                .build();
        List<CsvBean> personList = build.parse();
        personList.forEach(System.out::println);
    }
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