Class RecordReader
- java.lang.Object
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- com.ibm.jzos.RecordReader
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- All Implemented Interfaces:
- ZFileConstants
- Direct Known Subclasses:
- ZFileRecordReader
public abstract class RecordReader extends java.lang.Object implements ZFileConstants
This class provides record mode read access to z/OS datasets. Factory methodsnewReaderForDD
andnewReader(name, flags)
may be used to return an instance of an implementation subtype of this class.In order to provide more efficient dataset I/O performance, subtype implementations may use native BSAM I/O to read entire blocks from the underlying dataset into Java buffers and subsequently deblock records from these blocks. In addition, native calls to underlying I/O routines may be buffered and use overlapped I/O techniques if available to improve throughput and to reduce CPU overhead. Refer to
z/OS DFSMS Using Data Sets, SC26-7410
for more information.For datasets not supported by BSAM, such as VSAM, a call is made to an implementation subclass which uses a simple record-mode ZFile implementation. This means that this class will support reading from a VSAM dataset. The only public API to this class and its non-public implementation subclasses is via one of the static factory methods in this class; the implementation subclass instance returned is an implementation detail and is not controllable by the client, and may change in the future.
All sequential dataset organizations and record formats supported by ZFile (the IBM z/OS C library) are supported. For DSORG=PS datasets, best performance will be realized when using blocked records and large blocking factors.
Instances of ZFileException are thrown to report errors, but detailed codes and message text in these exceptions may reflect either BSAM access method errors or ZFile (C-library access method interface) errors.
Example: Read a dataset using a RecordReader via a DD name
String ddname = ZFile.allocDummyDDName(); String cmd = "alloc fi("+ddname+") da(HLQ.MYDATA) reuse shr msg(2)"; ZFile.bpxwdyn(cmd); RecordReader reader = null; try { reader = RecordReader.newReaderForDD(ddname); byte[] recordBuf = new byte[reader.getLrecl()]; while ((bytesRead = reader.read(recordBuf)) >= 0) { ... } } finally { if (reader != null) { try { reader.close(); } catch (ZFileException zfe) { zfe.printStackTrace(); // but continue } } try { ZFile.bpxwdyn("free fi(" + ddname + ") msg(2)"); } catch (RcException rce) { rce.printStackTrace(); // but continue } }
Example: Read a dataset using a RecordReader via a dataset name
There are two System properties that may be used to control the usage of BSAM implementation classes:RecordReader reader = null; try { reader = RecordReader.newReader("//my.dataset", ZFileConstants.FLAG_DISP_SHR); byte[] recordBuf = new byte[reader.getLrecl()]; while ((bytesRead = reader.read(recordBuf)) >= 0) { ... } } finally { if (reader != null) { reader.close(); } }
jzos.bsam.allow.abends
- if this is set totrue
, then ABENDs in the BSAM support will not be caught and thrown as ZFileExceptions. IBM Support may request this setting in order to get a dump.jzos.bsam.disable
- if this is set totrue
, then ZFile implementations will be used in all cases rather than direct BSAM implementation classes.
- Since:
- 2.4.1
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Field Summary
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Fields inherited from interface com.ibm.jzos.ZFileConstants
DEFAULT_EBCDIC_CODE_PAGE, DEVICE_DISK, DEVICE_DUMMY, DEVICE_HFS, DEVICE_HIPERSPACE, DEVICE_MEMORY, DEVICE_MSGFILE, DEVICE_OTHER, DEVICE_PRINTER, DEVICE_TAPE, DEVICE_TDQ, DEVICE_TERMINAL, DSORG_CONCAT, DSORG_HFS, DSORG_HIPER, DSORG_MEM, DSORG_PDS_DIR, DSORG_PDS_MEM, DSORG_PDSE, DSORG_PO, DSORG_PS, DSORG_TEMP, DSORG_VSAM, ERRNO_E_ABEND, ERRNO_E_DEFINEFILE, ERRNO_E_READERR, ERRNO_E_WRITEERR, ERRNO_EACCES, ERRNO_EILSEQ, ERRNO_EINVAL, ERRNO_EIO, ERRNO_EPERM, FLAG_DISP_MOD, FLAG_DISP_OLD, FLAG_DISP_SHR, FLAG_PDS_ENQ, LAST_OP_BSAM_BLDL, LAST_OP_BSAM_CLOSE, LAST_OP_BSAM_CLOSE_T, LAST_OP_BSAM_NOTE, LAST_OP_BSAM_OPEN, LAST_OP_BSAM_POINT, LAST_OP_BSAM_READ, LAST_OP_BSAM_STOW, LAST_OP_BSAM_WRITE, LAST_OP_C_CANNOT_EXTEND, LAST_OP_C_DBCS_SI_TRUNCATE, LAST_OP_C_DBCS_SO_TRUNCATE, LAST_OP_C_DBCS_TRUNCATE, LAST_OP_C_DBCS_UNEVEN, LAST_OP_C_FCBCHECK, LAST_OP_C_TRUNCATE, LAST_OP_HSP_CREATE, LAST_OP_HSP_DELETE, LAST_OP_HSP_EXTEND, LAST_OP_HSP_READ, LAST_OP_HSP_WRITE, LAST_OP_IO_CATALOG, LAST_OP_IO_DEVTYPE, LAST_OP_IO_LOCATE, LAST_OP_IO_OBTAIN, LAST_OP_IO_RDJFCB, LAST_OP_IO_RENAME, LAST_OP_IO_SCRATCH, LAST_OP_IO_SWAREQ, LAST_OP_IO_TRKCALC, LAST_OP_IO_UNCATALOG, LAST_OP_QSAM_FREEPOOL, LAST_OP_QSAM_GET, LAST_OP_QSAM_PUT, LAST_OP_QSAM_RELSE, LAST_OP_QSAM_TRUNC, LAST_OP_SVC99_ALLOC, LAST_OP_SVC99_ALLOC_NEW, LAST_OP_SVC99_UNALLOC, LAST_OP_TGET_READ, LAST_OP_TGET_WRITE, LAST_OP_VSAM_CLOSE, LAST_OP_VSAM_ENDREQ, LAST_OP_VSAM_ERASE, LAST_OP_VSAM_GENCB, LAST_OP_VSAM_GET, LAST_OP_VSAM_MODCB, LAST_OP_VSAM_OPEN_ESDS, LAST_OP_VSAM_OPEN_ESDS_PATH, LAST_OP_VSAM_OPEN_FAIL, LAST_OP_VSAM_OPEN_KSDS, LAST_OP_VSAM_OPEN_KSDS_PATH, LAST_OP_VSAM_OPEN_RRDS, LAST_OP_VSAM_POINT, LAST_OP_VSAM_PUT, LAST_OP_VSAM_SHOWCB, LAST_OP_VSAM_TESTCB, LOCATE_KEY_EQ, LOCATE_KEY_EQ_BWD, LOCATE_KEY_FIRST, LOCATE_KEY_GE, LOCATE_KEY_LAST, LOCATE_RBA_EQ, LOCATE_RBA_EQ_BWD, MODE_FLAG_APPEND, MODE_FLAG_READ, MODE_FLAG_UPDATE, MODE_FLAG_WRITE, OPEN_MODE_BINARY, OPEN_MODE_RECORD, OPEN_MODE_TEXT, RECFM_A, RECFM_B, RECFM_F, RECFM_M, RECFM_S, RECFM_U, RECFM_V, S_IRGRP, S_IROTH, S_IRUSR, S_IRWXG, S_IRWXO, S_IRWXU, S_ISGID, S_ISUID, S_ISVTX, S_IWGRP, S_IWOTH, S_IWUSR, S_IXGRP, S_IXOTH, S_IXUSR, SEEK_CUR, SEEK_END, SEEK_SET, VSAM_TYPE_ESDS, VSAM_TYPE_ESDS_PATH, VSAM_TYPE_KSDS, VSAM_TYPE_KSDS_PATH, VSAM_TYPE_NOTVSAM, VSAM_TYPE_RRDS
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method and Description abstract void
close()
Close the reader and underlying native file.boolean
getAutoFree()
Answer a flag that indicates whether the DD name associated with this file will automatically be freed when the file is closed.abstract int
getBlksize()
Answer the BLKSIZE, which is the maximum block length supported by the dataset.abstract java.lang.String
getDDName()
Answers the DD name used to open the underlying dataset.abstract java.lang.String
getDsn()
Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.abstract int
getLrecl()
Answer the LRECL, which is the maximum record length for variable length files.abstract java.lang.String
getRecfm()
Get the native file's record format.abstract int
getRecfmBits()
Answer the RECFM bitsstatic RecordReader
newReader(java.lang.String name, int flags)
Construct a new RecordReader for the given dataset name.static RecordReader
newReaderForDD(java.lang.String ddname)
Construct a new RecordReader on the given DD.abstract int
read(byte[] buf)
Read a record from the dataset into a buffer.abstract int
read(byte[] buf, int offset, int len)
Read a record from the dataset into a buffer.void
setAutoFree(boolean autoFree)
Sets a flag that will cause the DD to automatically be freed afterclose()
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Method Detail
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newReaderForDD
public static RecordReader newReaderForDD(java.lang.String ddname) throws ZFileException
Construct a new RecordReader on the given DD.The data definition must be 1-8 characters with some rules.
- Is 1 through 8 alphanumeric or national ($, #, @) characters.
- The first character must be alphabetic or national ($, #, @).
- Parameters:
ddname
- the previously allocated DD name that is associated with the dataset or file- Throws:
ZFileException
- if there was an error opening the dataset.
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newReader
public static RecordReader newReader(java.lang.String name, int flags) throws ZFileException, RcException
Construct a new RecordReader for the given dataset name.- Parameters:
name
- name of the file to open, in the same syntax asZFile.ZFile(String, String)
, the same syntax defined by the C-Library fopen() function. If the name specifies aDD:DDNAME
, then refer tonewReaderForDD(String)
for supported data definition syntaxflags
-- If the name specifies a
DD:DDNAME
, then flags must be 0. - If FLAG_DISP_SHR and the name refers to a dataset name, the dataset will be allocated with DISP=SHR.
- If FLAG_DISP_OLD or 0 and name refers to a dataset name, it will be allocated with DISP=OLD.
- If the name specifies a
- Throws:
ZFileException
- if the file could not be openedRcException
- if an error occurs when attempting to allocate the dataset, the exception fromZFile.bpxwdyn(String)
is thrown- Since:
- 2.4.2
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read
public abstract int read(byte[] buf) throws ZFileException
Read a record from the dataset into a buffer.- Parameters:
buf
- the byte array into which the bytes will be read- Returns:
- the number of bytes read, -1 if EOF encountered.
- Throws:
ZFileException
- if the native call fails
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read
public abstract int read(byte[] buf, int offset, int len) throws ZFileException
Read a record from the dataset into a buffer.- Parameters:
buf
- the byte array into which the bytes will be readoffset
- the offset, inclusive in buf to start reading byteslen
- the number of bytes to read- Returns:
- the number of bytes read, -1 if EOF encountered.
- Throws:
ZFileException
- if the native call fails
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close
public abstract void close() throws ZFileException
Close the reader and underlying native file.This will also free the associated DD if
getAutoFree()
is true.Note: close() must be issued by the same thread as the factory method that creates the instance object (opening the dataset). Reading can occur on any thread.
- Throws:
ZFileException
- if the native call fails
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getLrecl
public abstract int getLrecl()
Answer the LRECL, which is the maximum record length for variable length files.
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getBlksize
public abstract int getBlksize()
Answer the BLKSIZE, which is the maximum block length supported by the dataset.
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getRecfmBits
public abstract int getRecfmBits()
Answer the RECFM bits- See Also:
ZFile.getRecfmBits()
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getRecfm
public abstract java.lang.String getRecfm()
Get the native file's record format.- See Also:
ZFile.getRecfm()
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getDDName
public abstract java.lang.String getDDName()
Answers the DD name used to open the underlying dataset.- Returns:
- String ddname
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getDsn
public abstract java.lang.String getDsn()
Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.- Returns:
- String dataset name
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getAutoFree
public boolean getAutoFree()
Answer a flag that indicates whether the DD name associated with this file will automatically be freed when the file is closed. By default, this is true if this RecordReader was created usingnewReader()
supplying a dataset name.- Returns:
- boolean
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setAutoFree
public void setAutoFree(boolean autoFree)
Sets a flag that will cause the DD to automatically be freed afterclose()
.- See Also:
getAutoFree()
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