Spring-batch的文件footer处理是怎样的

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。

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;    }}

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