使用SuperCSV验证单次传递中的每个字段 [英] Validate every field in a single pass with SuperCSV
问题描述
我试图使用SuperCSV从数据库写入大量行（约2百万）到CSV文件。我需要对每个单元格进行验证，因为它是写的，而内置的CellProcessor做得非常好。我想捕获CellProcessors抛出的所有异常，以便我可以回到源数据并进行更改。
I'm trying to write a large number of rows (~2 million) from a database to a CSV file using SuperCSV. I need to perform validation on each cell as it is written, and the built-in CellProcessors do very nicely. I want to capture all the exceptions that are thrown by the CellProcessors so that I can go back to the source data and make changes.
问题是，当有多个单行中的错误（例如，第一个值超出范围，第二个值为空，但不应为），则只有第一个CellProcessor将执行，因此我只会看到其中一个错误。我想在一个单一的过程中处理整个文件，并在它的末尾有一套完整的异常。
The problem is that when there are multiple errors in a single row (e.g. The first value is out of range, the second value is null but shouldn't be), only the first CellProcessor will execute, and so I'll only see one of the errors. I want to process the whole file in a single pass, and have a complete set of exceptions at the end of it.
这是我试图的方法：
for (Row row : rows) {
try {
csvBeanWriter.write(row, HEADER_MAPPINGS, CELL_PROCESSORS);
} catch (SuperCsvCellProcessorException e) {
log(e);
}
}
如何实现？谢谢！
编辑：这是我写的类似于Hound Dog's的代码，以防它帮助任何人：
Here is the code I wrote that's similar to Hound Dog's, in case it helps anyone:
import java.util.List;
import org.supercsv.cellprocessor.CellProcessorAdaptor;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.exception.SuperCsvCellProcessorException;
import org.supercsv.util.CsvContext;
public class ExceptionCapturingCellProcessor extends CellProcessorAdaptor {
private final List<Exception> exceptions;
private final CellProcessor current;
public ExceptionCapturingCellProcessor(CellProcessor current, CellProcessor next, List<Exception> exceptions) {
super(next);
this.exceptions = exceptions;
this.current = current;
}
@Override
public Object execute(Object value, CsvContext context) {
// Check input is not null
try {
validateInputNotNull(value, context);
} catch (SuperCsvCellProcessorException e) {
exceptions.add(e);
}
// Execute wrapped CellProcessor
try {
current.execute(value, context);
} catch (SuperCsvCellProcessorException e) {
exceptions.add(e);
}
return next.execute(value, context);
}
}
推荐答案
I建议您编写自定义CellProcessor 来实现此目的。以下处理器可以放置在每个CellProcessor链的开头 - 它将简单地委派给在其后链接的处理器，并且将抑制任何单元处理异常。
I'd recommend writing a custom CellProcessor to achieve this. The following processor can be placed at the start of each CellProcessor chain - it will simply delegate to the processor chained after it, and will suppress any cell processing exceptions.
package example;
import java.util.ArrayList;
import java.util.List;
import org.supercsv.cellprocessor.CellProcessorAdaptor;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.exception.SuperCsvCellProcessorException;
import org.supercsv.util.CsvContext;
public class SuppressException extends CellProcessorAdaptor {
public static List<SuperCsvCellProcessorException> SUPPRESSED_EXCEPTIONS =
new ArrayList<SuperCsvCellProcessorException>();
public SuppressException(CellProcessor next) {
super(next);
}
public Object execute(Object value, CsvContext context) {
try {
// attempt to execute the next processor
return next.execute(value, context);
} catch (SuperCsvCellProcessorException e) {
// save the exception
SUPPRESSED_EXCEPTIONS.add(e);
// and suppress it (null is written as "")
return null;
}
}
}
：
package example;
import java.io.StringWriter;
import java.util.Arrays;
import java.util.List;
import org.supercsv.cellprocessor.constraint.NotNull;
import org.supercsv.cellprocessor.constraint.StrMinMax;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.exception.SuperCsvCellProcessorException;
import org.supercsv.io.CsvBeanWriter;
import org.supercsv.io.ICsvBeanWriter;
import org.supercsv.prefs.CsvPreference;
public class TestSuppressExceptions {
private static final CellProcessor[] PROCESSORS = {
new SuppressException(new StrMinMax(0, 4)),
new SuppressException(new NotNull()) };
private static final String[] HEADER = { "name", "age" };
public static void main(String[] args) throws Exception {
final StringWriter stringWriter = new StringWriter();
ICsvBeanWriter beanWriter = null;
try {
beanWriter = new CsvBeanWriter(stringWriter,
CsvPreference.STANDARD_PREFERENCE);
beanWriter.writeHeader(HEADER);
// set up the data
Person valid = new Person("Rick", 43);
Person nullAge = new Person("Lori", null);
Person totallyInvalid = new Person("Shane", null);
Person valid2 = new Person("Carl", 12);
List<Person> people = Arrays.asList(valid, nullAge, totallyInvalid,
valid2);
for (Person person : people) {
beanWriter.write(person, HEADER, PROCESSORS);
if (!SuppressException.SUPPRESSED_EXCEPTIONS.isEmpty()) {
System.out.println("Suppressed exceptions for row "
+ beanWriter.getRowNumber() + ":");
for (SuperCsvCellProcessorException e :
SuppressException.SUPPRESSED_EXCEPTIONS) {
System.out.println(e);
}
// clear ready for next row
SuppressException.SUPPRESSED_EXCEPTIONS.clear();
}
}
} finally {
beanWriter.close();
}
// CSV will have empty columns for invalid data
System.out.println(stringWriter);
}
}
异常输出（第4行有两个异常，每列一个）：
Here's the suppressed exceptions output (row 4 has two exceptions, one for each column):
Suppressed exceptions for row 3:
org.supercsv.exception.SuperCsvConstraintViolationException: null value
encountered processor=org.supercsv.cellprocessor.constraint.NotNull
context={lineNo=3, rowNo=3, columnNo=2, rowSource=[Lori, null]}
Suppressed exceptions for row 4:
org.supercsv.exception.SuperCsvConstraintViolationException: the length (5)
of value 'Shane' does not lie between the min (0) and max (4) values (inclusive)
processor=org.supercsv.cellprocessor.constraint.StrMinMax
context={lineNo=4, rowNo=4, columnNo=2, rowSource=[Shane, null]}
org.supercsv.exception.SuperCsvConstraintViolationException: null value
encountered processor=org.supercsv.cellprocessor.constraint.NotNull
context={lineNo=4, rowNo=4, columnNo=2, rowSource=[Shane, null]}
以及CSV输出
name,age
Rick,43
Lori,
,
Carl,12
请注意无效值如何写为，因为 SuppressException 处理器为这些值返回了 null （不是你将使用CSV输出，因为它无效！）。
Notice how the invalid values were written as "" because the SuppressException processor returned null for those values (not that you'd use the CSV output anyway, as it's not valid!).
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