无法使用 Apache Commons 解析来自 github CSV URL 的标头

Question

我正在尝试使用 Apache commons csv 库从 github 访问 CSV 文件 url 中存在的每条记录的标头值。

这是我的代码：

@Service
public class CoronaVirusDataService {

    private static String virus_data_url = "https://raw.githubusercontent.com/CSSEGISandData/COVID-19/Aysen_Chile_07032021/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_confirmed_global.csv";
    
    @PostConstruct
    public void getVirusData()
    {
        try
        {
        URL url = new URL(virus_data_url);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        BufferedReader in = new BufferedReader( new InputStreamReader(con.getInputStream()));
        
        while((in.readLine()) != null)
        {
            StringReader csvReader = new StringReader(in.readLine());
            Iterable<CSVRecord> records = CSVFormat.DEFAULT.withFirstRecordAsHeader().parse(csvReader);
            for (CSVRecord record : records) {
                String country = record.get("Country/Region");
                System.out.println(country);
            }       
        }
        in.close();
        }
        catch(Exception e) 
        {
            e.printStackTrace();
        }
    }
}

当我运行应用程序时出现此错误：

java.lang.IllegalArgumentException: A header name is missing in [, Afghanistan, 33.93911, 67.709953, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 4, 4, 4, 5, 7, 8, 11, 12, 13, 15, 16, 18, 20, 24, 25, 29, 30, 34, 41, 43, 76, 80, 91, 107, 118, 146, 175, 197, 240, 275, 300, 338, 368, 424, 445, 485, 532, 556, 608, 666, 715, 785, 841, 907, 934, 997, 1027, 1093]
at org.apache.commons.csv.CSVParser.createHeaders(CSVParser.java:501)
at org.apache.commons.csv.CSVParser.<init>(CSVParser.java:412)
at org.apache.commons.csv.CSVParser.<init>(CSVParser.java:378)
at org.apache.commons.csv.CSVFormat.parse(CSVFormat.java:1157)
at com.p1.Services.CoronaVirusDataService.getVirusData(CoronaVirusDataService.java:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)

Answer 1

如果您想将第一行作为标题读取，则不应逐行读取，因为 Apache CSV 会尝试将每一行作为标题读取。所以抛出异常。相反，您应该通过 reader 来读取数据。 下面的代码工作正常。

@Service
public class CoronaVirusDataService {

    private static String virus_data_url = "https://raw.githubusercontent.com/CSSEGISandData/COVID-19/Aysen_Chile_07032021/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_confirmed_global.csv";
    
    @PostConstruct
    public void getVirusData()
    {
        try
        {
        URL url = new URL(virus_data_url);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        BufferedReader in = new BufferedReader( new InputStreamReader(con.getInputStream()));

            Iterable<CSVRecord> records = CSVFormat.DEFAULT.withFirstRecordAsHeader().parse(in);
            for (CSVRecord record : records) {
                String country = record.get("Country/Region");
                System.out.println(country);
            }       
   
        in.close();
        }
        catch(Exception e) 
        {
            e.printStackTrace();
        }
    }
}

Answer 2

您想要解析带有标头和标准 CSV 格式的 HTTP 文件。如果您尝试在 Java 中进行解析，则代码会很长。但是，使用开源 Java 包 SPL 很容易完成这项工作。你只需要一行代码：

	A
1	=httpfile("https://raw.githubusercontent.com/CSSEGISandData/COVID-/Aysen_Chile_07032021/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_confirmed_global.csv") .import@ct(Country/Region)

SPL 提供 JDBC 驱动程序供 Java 调用。只需将上述 SPL 脚本存储为 httpcsv.splx 并在调用存储过程时在 Java 中调用它：

…
Class.forName("com.esproc.jdbc.InternalDriver");
con= DriverManager.getConnection("jdbc:esproc:local://");
st=con.prepareCall("call httpcsv()");
st.execute();
…

或者像我们执行 SQL 语句的方式在 Java 程序中执行 SPL 字符串：

…
st = con.prepareStatement("==httpfile(\"https://raw.githubusercontent.com/CSSEGISandData/COVID-19/Aysen_Chile_07032021/csse_covid_19_data/csse_covid_19_time_series/time_series_covid19_confirmed_global.csv\").import@ct(Country/Region)");
st.execute();
…