public static final String ID_PAYLOAD_FIELD = "_ID";

public static final String ID_PAYLOAD_TERM = "_ID";

public static final Term ID_TERM = new Term(ID_PAYLOAD_TERM, ID_PAYLOAD_FIELD);

//声明一个特殊的TokenStream，它只生成一个词(Term)，就是那个特殊的词，在特殊的域里面。

static class SinglePayloadTokenStream extends TokenStream { 
    private Token token; 
    private boolean returnToken = false;

SinglePayloadTokenStream(String idPayloadTerm) { 
        char[] term = idPayloadTerm.toCharArray(); 
        token = new Token(term, 0, term.length, 0, term.length); 
    }

void setPayloadValue(byte[] value) { 
        token.setPayload(new Payload(value)); 
        returnToken = true; 
    }

public Token next() throws IOException { 
        if (returnToken) { 
            returnToken = false; 
            return token; 
        } else { 
            return null; 
        } 
    } 
}

//对于每一篇文档，都让它包含这个特殊的词，在特殊的域里面

SinglePayloadTokenStream singlePayloadTokenStream = new SinglePayloadTokenStream(ID_PAYLOAD_TERM); 
singlePayloadTokenStream.setPayloadValue(long2bytes(id)); 
doc.add(new Field(ID_PAYLOAD_FIELD, singlePayloadTokenStream));

//每当得到一个Lucene的文档号时，通过以下的方式得到payload里面的文档号

long id = 0; 
TermPositions tp = reader.termPositions(ID_PAYLOAD_TERM); 
boolean ret = tp.skipTo(docID); 
tp.nextPosition(); 
int payloadlength = tp.getPayloadLength(); 
byte[] payloadBuffer = new byte[payloadlength]; 
tp.getPayload(payloadBuffer, 0); 
id = bytes2long(payloadBuffer); 
tp.close();

FieldInfos.read(IndexInput, String)

• int firstInt = input.readVInt();
• size = input.readVInt();
• for (int i = 0; i < size; i++)
  • String name = input.readString();
  • byte bits = input.readByte();
  • boolean isIndexed = (bits & IS_INDEXED) != 0;
  • boolean storeTermVector = (bits & STORE_TERMVECTOR) != 0;
  • boolean storePositionsWithTermVector = (bits & STORE_POSITIONS_WITH_TERMVECTOR) != 0;
  • boolean storeOffsetWithTermVector = (bits & STORE_OFFSET_WITH_TERMVECTOR) != 0;
  • boolean omitNorms = (bits & OMIT_NORMS) != 0;
  • boolean storePayloads = (bits & STORE_PAYLOADS) != 0;
  • boolean omitTermFreqAndPositions = (bits & OMIT_TERM_FREQ_AND_POSITIONS) != 0;