public abstract class RecordReader extends java.lang.Object implements ZFileConstants
newReaderForDD
and
newReader(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. 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
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();
}
}
There are two System properties that may be used to control the usage of BSAM implementation classes:
jzos.bsam.allow.abends
- if this is set to true, 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 to true, then ZFile implementations will be used in all cases rather than direct BSAM implementation classes.
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
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 bits
|
static 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 after
close() . |
public static RecordReader newReaderForDD(java.lang.String ddname) throws ZFileException
ddname
- the previously allocated DD name that is associated with the dataset or file.ZFileException
public static RecordReader newReader(java.lang.String name, int flags) throws ZFileException, RcException
name
- the name of the file to open, in the same syntax as ZFile.ZFile(String, String)
, the
same syntax defined by the C-Library fopen() function.flags
- DD:DDNAME, then flags must be 0.
ZFileException
- if the file could not be openedRcException
- if an error occurs when attempting to allocate the dataset,
the exception from ZFile.bpxwdyn(String)
is thrownpublic abstract int read(byte[] buf) throws ZFileException
buf
- the byte array into which the bytes will be readZFileException
- if the native call failspublic abstract int read(byte[] buf, int offset, int len) throws ZFileException
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 readZFileException
- if the native call failspublic abstract void close() throws ZFileException
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.
ZFileException
- if the native call failspublic abstract int getLrecl()
public abstract int getBlksize()
public abstract int getRecfmBits()
ZFile.getRecfmBits()
public abstract java.lang.String getRecfm()
ZFile.getRecfm()
public abstract java.lang.String getDDName()
public abstract java.lang.String getDsn()
public boolean getAutoFree()
newReader()
supplying a dataset name.public void setAutoFree(boolean autoFree)
close()
.getAutoFree()