XrefTrailerResolver (PDFBox reactor 2.0.4 API)

java.lang.Object
- org.apache.pdfbox.pdfparser.XrefTrailerResolver

```
public class XrefTrailerResolver
extends Object
```
This class will collect all XRef/trailer objects and creates correct xref/trailer information after all objects are read using startxref and 'Prev' information (unused XRef/trailer objects are discarded). In case of missing startxref or wrong startxref pointer all XRef/trailer objects are used to create xref table / trailer dictionary in order they occur. For each new xref object/XRef stream method nextXrefObj(long, XRefType) must be called with start byte position. All following calls to setXRef(COSObjectKey, long) or setTrailer(COSDictionary) will add the data for this byte position. After all objects are parsed the startxref position must be provided using setStartxref(long). This is used to build the chain of active xref/trailer objects used for creating document trailer and xref table.

Author:

Timo Böhme

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class XrefTrailerResolver.XRefType
The XRefType of a trailer.

Nested Classes
Modifier and Type	Class and Description
`static class`	`XrefTrailerResolver.XRefType` The XRefType of a trailer.

Constructor Summary

Constructors
Constructor and Description

XrefTrailerResolver()

Constructors
Constructor and Description
`XrefTrailerResolver()`

Method Summary

Methods
Modifier and Type	Method and Description
`Set<Long>`	`getContainedObjectNumbers(int objstmObjNr)` Returns object numbers which are referenced as contained in object stream with specified object number.
`COSDictionary`	`getCurrentTrailer()` Returns the trailer last set by `setTrailer(COSDictionary)`.
`COSDictionary`	`getFirstTrailer()` Returns the first trailer if at least one exists.
`COSDictionary`	`getLastTrailer()` Returns the last trailer if at least one exists.
`COSDictionary`	`getTrailer()` Gets the resolved trailer.
`int`	`getTrailerCount()` Returns the count of trailers.
`Map<COSObjectKey,Long>`	`getXrefTable()` Gets the resolved xref table.
`XrefTrailerResolver.XRefType`	`getXrefType()` Returns the XRefTxpe of the resolved trailer.
`void`	`nextXrefObj(long startBytePos, XrefTrailerResolver.XRefType type)` Signals that a new XRef object (table or stream) starts.
`void`	`setStartxref(long startxrefBytePosValue)` Sets the byte position of the first XRef (has to be called after very last startxref was read).
`void`	`setTrailer(COSDictionary trailer)` Adds trailer information for current XRef object.
`void`	`setXRef(COSObjectKey objKey, long offset)` Populate XRef HashMap of current XRef object.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - XrefTrailerResolver
```
public XrefTrailerResolver()
```
- Method Detail
  - getFirstTrailer
```
public final COSDictionary getFirstTrailer()
```
    Returns the first trailer if at least one exists.
    
    Returns:
    the first trailer or null
  - getLastTrailer
```
public final COSDictionary getLastTrailer()
```
    Returns the last trailer if at least one exists.
    
    Returns:
    the last trailer ir null
  - getTrailerCount
```
public final int getTrailerCount()
```
    Returns the count of trailers.
    
    Returns:
    the count of trailers.
  - nextXrefObj
```
public void nextXrefObj(long startBytePos,
               XrefTrailerResolver.XRefType type)
```
    Signals that a new XRef object (table or stream) starts.
    
    Parameters:
    startBytePos - the offset to start at
    type - the type of the Xref object
  - getXrefType
```
public XrefTrailerResolver.XRefType getXrefType()
```
    Returns the XRefTxpe of the resolved trailer.
    
    Returns:
    the XRefType or null.
  - setXRef
```
public void setXRef(COSObjectKey objKey,
           long offset)
```
    Populate XRef HashMap of current XRef object. Will add an Xreftable entry that maps ObjectKeys to byte offsets in the file.
    
    Parameters:
    objKey - The objkey, with id and gen numbers
    offset - The byte offset in this file
  - setTrailer
```
public void setTrailer(COSDictionary trailer)
```
    Adds trailer information for current XRef object.
    
    Parameters:
    trailer - the current document trailer dictionary
  - getCurrentTrailer
```
public COSDictionary getCurrentTrailer()
```
    Returns the trailer last set by setTrailer(COSDictionary).
    
    Returns:
    the current trailer.
  - setStartxref
```
public void setStartxref(long startxrefBytePosValue)
```
    Sets the byte position of the first XRef (has to be called after very last startxref was read). This is used to resolve chain of active XRef/trailer. In case startxref position is not found we output a warning and use all XRef/trailer objects combined in byte position order. Thus for incomplete PDF documents with missing startxref one could call this method with parameter value -1.
    
    Parameters:
    startxrefBytePosValue - starting position of the first XRef
  - getTrailer
```
public COSDictionary getTrailer()
```
    Gets the resolved trailer. Might return null in case setStartxref(long) was not called before.
    
    Returns:
    the trailer if available
  - getXrefTable
```
public Map<COSObjectKey,Long> getXrefTable()
```
    Gets the resolved xref table. Might return null in case setStartxref(long) was not called before.
    
    Returns:
    the xrefTable if available
  - getContainedObjectNumbers
```
public Set<Long> getContainedObjectNumbers(int objstmObjNr)
```
    Returns object numbers which are referenced as contained in object stream with specified object number. This will scan resolved xref table for all entries having negated stream object number as value.
    
    Parameters:
    objstmObjNr - object number of object stream for which contained object numbers should be returned
    
    Returns:
    set of object numbers referenced for given object stream or null if setStartxref(long) was not called before so that no resolved xref table exists

Class XrefTrailerResolver

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

XrefTrailerResolver

Method Detail

getFirstTrailer

getLastTrailer

getTrailerCount

nextXrefObj

getXrefType

setXRef

setTrailer

getCurrentTrailer

setStartxref

getTrailer

getXrefTable

getContainedObjectNumbers