我正在将FileWritingMessageHandler与自定义FileNameGenerator结合使用，该自定义log4j会间隔生成新文件名（类似于@Slf4j
@Getter
@AllArgsConstructor
public class RolloverFileNameGenerator extends AbstractExpressionEvaluator implements FileNameGenerator {
private final Map<CachedFileEvaluation, String> cache;
private final RoundedBucketIntervalCalculator intervalCalculator;
private final Map<String, Object> commonContext;
private final Expression nameExpression;
@SuppressWarnings("unchecked")
public RolloverFileNameGenerator(final RoundedBucketIntervalCalculator intervalCalculator,
final String nameExpression, final Map<String, Object> context, final int cacheMaxSize) {
this(new LRUMap(cacheMaxSize), intervalCalculator, context, EXPRESSION_PARSER.parseExpression(nameExpression));
}
@SuppressWarnings("unchecked")
public RolloverFileNameGenerator(final RoundedBucketIntervalCalculator intervalCalculator, final String nameExpression, final Map<String, Object> context) {
this(null, intervalCalculator, context, EXPRESSION_PARSER.parseExpression(nameExpression));
}
@Override
public String generateFileName(final Message<?> message) {
return generateFileName(message, DateTime.now());
}
public String generateFileName(final Message<?> message, final DateTime dateTime) {
final Interval interval = intervalCalculator.getInterval(dateTime);
if (cache == null) {
return evaluateFilenameFromMessage(message, interval);
}
final Optional<String> cached = cache.entrySet().stream()
.filter(entry -> entry.getKey().isBetweenInclusive(dateTime))
.findFirst()
.map(Map.Entry::getValue);
return cached.orElseGet(() -> {
final String evaluatedValue = evaluateFilenameFromMessage(message, interval);
cache.putIfAbsent(new CachedFileEvaluation(interval), evaluatedValue);
return evaluatedValue;
});
}
private String evaluateFilenameFromMessage(final Message<?> message, final Interval interval) {
final Object evaluated = this.evaluateExpression(nameExpression, new RolloverEvaluationContext(commonContext, interval, message));
if (evaluated == null) {
throw new IllegalArgumentException("Evaluated expression is valid, but it resulted with a null");
}
if (!(evaluated instanceof String)) {
throw new IllegalArgumentException(String.format("Evaluated expression is valid, but it didn't result in a String. Evaluated result: (%s) %s", evaluated.getClass(), evaluated));
}
return (String) evaluated;
}
@Data
@AllArgsConstructor
public class CachedFileEvaluation {
private Interval interval;
public boolean isBetweenInclusive(final DateTime date) {
return interval.contains(date) || interval.getEnd().isEqual(date);
}
}
@Getter
@AllArgsConstructor
private class RolloverEvaluationContext {
private final Map<String, Object> ctx;
private final Interval interval;
private final Message<?> message;
}
}
的滚动文件追加程序）。
@Bean
@ConditionalOnProperty(prefix = "com.github.alturkovic.rollover.writer", name = "initialize", havingValue = "true", matchIfMissing = true)
public FileWritingMessageHandler fileWritingMessageHandler(final RolloverFileNameGenerator rolloverFileNameGenerator) {
final Writer writer = properties.getWriter();
final FileWritingMessageHandler handler = new FileWritingMessageHandler(new File(properties.getDirectory()));
handler.setAppendNewLine(writer.isAppendNewLine());
handler.setAutoCreateDirectory(writer.isAutoCreateDirectory());
handler.setFileExistsMode(writer.getMode());
handler.setFlushInterval(writer.getFlushInterval());
handler.setFileNameGenerator(rolloverFileNameGenerator);
handler.setOutputChannelName("nullChannel");
return handler;
}
根据我的配置：
FileWritingMessageHandler每次必须创建一个新文件时，我都想向其写入CSV标头。我调查了FileWritingMessageHandler，但不知道如何完成自己要完成的工作。
如果可以在不更改CREATE VIEW view_grades AS
IF test_special_role()
THEN SELECT * FROM "Grades"
ELSE SELECT * FROM "Grades" WHERE uid=get_current_uid() ...
END IF;
源代码的情况下做到这一点，有人可以向我指出正确的方向吗？
答案 0 :(得分：0)
您可以保留一些状态，只需将标题写在RolloverFileNameGenerator.generateFileName()中即可。
if (!newName.equals(lastName) {
// write header
}