这篇文章给大家介绍Spring-batch的文件footer处理是怎样的，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。
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Spring-batch对文件处理时,可以是：
1）单纯body文件数据形式；
2）header+body文件数据形式。
但是当文件数据是header+body+footer的场合，对于footer的处理则没有很好的方式。
重写FileItemReader类实现对于footer的Callback处理。（类似skippedLinesCallback）
1）FileItemReader
2）FileReadFooterHandler
3）job.xml
package l.c.w;
import java.io.BufferedReader;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ReaderNotOpenException;
import org.springframework.batch.item.file.BufferedReaderFactory;
import org.springframework.batch.item.file.DefaultBufferedReaderFactory;
import org.springframework.batch.item.file.FlatFileItemReader;
import org.springframework.batch.item.file.FlatFileParseException;
import org.springframework.batch.item.file.LineCallbackHandler;
import org.springframework.batch.item.file.LineMapper;
import org.springframework.batch.item.file.NonTransientFlatFileException;
import org.springframework.batch.item.file.ResourceAwareItemReaderItemStream;
import org.springframework.batch.item.file.separator.RecordSeparatorPolicy;
import org.springframework.batch.item.file.separator.SimpleRecordSeparatorPolicy;
import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
/**
* Restartable {@link ItemReader} that reads lines from input {@link #setResource(Resource)}. Line is defined by the
* {@link #setRecordSeparatorPolicy(RecordSeparatorPolicy)} and mapped to item using {@link #setLineMapper(LineMapper)}.
* If an exception is thrown during line mapping it is rethrown as {@link FlatFileParseException} adding information
* about the problematic line and its line number.
*
* @author Robert Kasanicky
* @author wcl
*/
public class FileItemReader extends AbstractItemCountingItemStreamItemReader implements
ResourceAwareItemReaderItemStream, InitializingBean {
private static final Log logger = LogFactory.getLog(FileItemReader.class);
// default encoding for input files
public static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
private RecordSeparatorPolicy recordSeparatorPolicy = new SimpleRecordSeparatorPolicy();
private Resource resource;
private BufferedReader reader;
private int lineCount = 0;
private String[] comments = new String[] { "#" };
private boolean noInput = false;
private String encoding = DEFAULT_CHARSET;
private LineMapper lineMapper;
private int linesToSkip = 0;
private LineCallbackHandler skippedLinesCallback;
private boolean strict = true;
private BufferedReaderFactory bufferedReaderFactory = new DefaultBufferedReaderFactory();
private FileReadFooterHandler fileReadFooterHandler;
private List footerLines = null;
public FileItemReader() {
setName(ClassUtils.getShortName(FlatFileItemReader.class));
}
/**
* In strict mode the reader will throw an exception on
* {@link #open(org.springframework.batch.item.ExecutionContext)} if the input resource does not exist.
* @param strict true by default
*/
public void setStrict(boolean strict) {
this.strict = strict;
}
/**
* @param skippedLinesCallback will be called for each one of the initial skipped lines before any items are read.
*/
public void setSkippedLinesCallback(LineCallbackHandler skippedLinesCallback) {
this.skippedLinesCallback = skippedLinesCallback;
}
/**
* Public setter for the number of lines to skip at the start of a file. Can be used if the file contains a header
* without useful (column name) information, and without a comment delimiter at the beginning of the lines.
*
* @param linesToSkip the number of lines to skip
*/
public void setLinesToSkip(int linesToSkip) {
this.linesToSkip = linesToSkip;
}
/**
* Setter for line mapper. This property is required to be set.
* @param lineMapper maps line to item
*/
public void setLineMapper(LineMapper lineMapper) {
this.lineMapper = lineMapper;
}
/**
* Setter for the encoding for this input source. Default value is {@link #DEFAULT_CHARSET}.
*
* @param encoding a properties object which possibly contains the encoding for this input file;
*/
public void setEncoding(String encoding) {
this.encoding = encoding;
}
/**
* Factory for the {@link BufferedReader} that will be used to extract lines from the file. The default is fine for
* plain text files, but this is a useful strategy for binary files where the standard BufferedReaader from java.io
* is limiting.
*
* @param bufferedReaderFactory the bufferedReaderFactory to set
*/
public void setBufferedReaderFactory(BufferedReaderFactory bufferedReaderFactory) {
this.bufferedReaderFactory = bufferedReaderFactory;
}
/**
* Setter for comment prefixes. Can be used to ignore header lines as well by using e.g. the first couple of column
* names as a prefix.
*
* @param comments an array of comment line prefixes.
*/
public void setComments(String[] comments) {
this.comments = new String[comments.length];
System.arraycopy(comments, 0, this.comments, 0, comments.length);
}
/**
* Public setter for the input resource.
*/
@Override
public void setResource(Resource resource) {
this.resource = resource;
}
/**
* Public setter for the recordSeparatorPolicy. Used to determine where the line endings are and do things like
* continue over a line ending if inside a quoted string.
*
* @param recordSeparatorPolicy the recordSeparatorPolicy to set
*/
public void setRecordSeparatorPolicy(RecordSeparatorPolicy recordSeparatorPolicy) {
this.recordSeparatorPolicy = recordSeparatorPolicy;
}
/**
* Public setter for the fileReadFooterHandler.
*
* @param fileReadFooterHandler the fileReadFooterHandler to set
*/
public void setFileReadFooterHandler(FileReadFooterHandler fileReadFooterHandler) {
this.fileReadFooterHandler = fileReadFooterHandler;
}
/**
* @return string corresponding to logical record according to
* {@link #setRecordSeparatorPolicy(RecordSeparatorPolicy)} (might span multiple lines in file).
*/
@Override
protected T doRead() throws Exception {
if (noInput) {
return null;
}
String line = readLine();
if (line == null) {
return null;
}
else {
try {
return lineMapper.mapLine(line, lineCount);
}
catch (Exception ex) {
throw new FlatFileParseException("Parsing error at line: " + lineCount + " in resource=["
+ resource.getDescription() + "], input=[" + line + "]", ex, line, lineCount);
}
}
}
/**
* @return next line (skip comments).getCurrentResource
*/
private String readLine() {
if (reader == null) {
throw new ReaderNotOpenException("Reader must be open before it can be read.");
}
String line = null;
try {
line = this.reader.readLine();
if (line == null) {
return null;
}
lineCount++;
while (isComment(line) || isFooter(line)) {
line = reader.readLine();
if (line == null) {
return null;
}
lineCount++;
}
line = applyRecordSeparatorPolicy(line);
}
catch (IOException e) {
// Prevent IOException from recurring indefinitely
// if client keeps catching and re-calling
noInput = true;
throw new NonTransientFlatFileException("Unable to read from resource: [" + resource + "]", e, line,
lineCount);
}
return line;
}
private boolean isComment(String line) {
for (String prefix : comments) {
if (line.startsWith(prefix)) {
return true;
}
}
return false;
}
private boolean isFooter(String line) {
if (footerLines == null) {
footerLines = fileReadFooterHandler.footerLines();
}
for (String footer : footerLines) {
if (line.equals(footer)) {
return true;
}
}
return false;
}
@Override
protected void doClose() throws Exception {
lineCount = 0;
if (reader != null) {
reader.close();
}
}
@Override
protected void doOpen() throws Exception {
Assert.notNull(resource, "Input resource must be set");
Assert.notNull(recordSeparatorPolicy, "RecordSeparatorPolicy must be set");
noInput = true;
if (!resource.exists()) {
if (strict) {
throw new IllegalStateException("Input resource must exist (reader is in 'strict' mode): " + resource);
}
logger.warn("Input resource does not exist " + resource.getDescription());
return;
}
if (!resource.isReadable()) {
if (strict) {
throw new IllegalStateException("Input resource must be readable (reader is in 'strict' mode): "
+ resource);
}
logger.warn("Input resource is not readable " + resource.getDescription());
return;
}
reader = bufferedReaderFactory.create(resource, encoding);
for (int i = 0; i < linesToSkip; i++) {
String line = readLine();
if (skippedLinesCallback != null) {
skippedLinesCallback.handleLine(line);
}
}
noInput = false;
}
@Override
public void afterPropertiesSet() throws Exception {
Assert.notNull(lineMapper, "LineMapper is required");
}
@Override
protected void jumpToItem(int itemIndex) throws Exception {
for (int i = 0; i < itemIndex; i++) {
readLine();
}
}
private String applyRecordSeparatorPolicy(String line) throws IOException {
String record = line;
while (line != null && !recordSeparatorPolicy.isEndOfRecord(record)) {
line = this.reader.readLine();
if (line == null) {
if (StringUtils.hasText(record)) {
// A record was partially complete since it hasn't ended but
// the line is null
throw new FlatFileParseException("Unexpected end of file before record complete", record, lineCount);
}
else {
// Record has no text but it might still be post processed
// to something (skipping preProcess since that was already
// done)
break;
}
}
else {
lineCount++;
}
record = recordSeparatorPolicy.preProcess(record) + line;
}
return recordSeparatorPolicy.postProcess(record);
}
} package l.c.w;
import java.io.RandomAccessFile;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import l.c.w.common.contants.JobConstants;
import l.c.w.common.utils.StringUtil;
import org.springframework.batch.core.StepExecution;
import org.springframework.batch.core.annotation.BeforeStep;
/**
*
* footer line skip.
*
* @author wcl
*
*/
public class FileReadFooterHandler {
// default encoding for input files
public static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
private StepExecution stepExecution;
private String charset = DEFAULT_CHARSET;
private int lines = 0;
@BeforeStep
public void beforeStep(StepExecution stepExecution) throws Exception {
this.stepExecution = stepExecution;
// resource
String fileName = this.stepExecution.getJobExecution().getJobParameters().
getString("inFile");
List footers = new ArrayList();
setFooterLines(footers, fileName);
this.stepExecution.getExecutionContext().put("footer_line_list", footers);
}
@SuppressWarnings("unchecked")
public List footerLines() {
List footers = (List) this.stepExecution.getExecutionContext().get(
"footer_line_list");
return footers;
}
/**
* footer line data get.
*
* @param footers
* @throws Exception
*/
private void setFooterLines(List footers, String fileName) throws Exception {
RandomAccessFile raf = null;
try {
raf = new RandomAccessFile(fileName, "r");
long len = raf.length();
if (len == 0L) {
return;
}
long pos = len - 1;
while (pos > 0 && lines > 0) {
pos--;
raf.seek(pos);
if (raf.read() == '\n' || raf.read() == '\r') {
String line = raf.readLine();
if (StringUtil.isNotEmpty(line)) {
footers.add(0, new String(line.getBytes("ISO-8859-1"), charset));
lines--;
}
}
}
} finally {
if (raf != null) {
raf.close();
}
}
}
/**
* Setter for the charset for this input source. Default value is {@link #DEFAULT_CHARSET}.
*
* @param encoding a properties object which possibly contains the encoding for this input file;
*/
public void setCharset(String charset) {
this.charset = charset;
}
/**
* Public setter for footer line.
*/
public void setLines(int lines) {
this.lines = lines;
}
} 
