mysql 协议的ColumnDefinition包及解析代码详情

git

https://github.com/sea-boat/mysql-protocol

概况

ColumnDefinition包属于服务端返回ResultSet时的其中一部分包，用于描述结果集的字段信息。

mysql通信报文结构

类型	名字	描述
int<3>	payload长度	按照the least significant byte first存储，3个字节的payload和1个字节的序列号组合成报文头
int<1>	序列号
string	payload	报文体，长度即为前面指定的payload长度

ColumnDefinition包

Payload

lenenc_str     catalog
lenenc_str     schema
lenenc_str     table
lenenc_str     org_table
lenenc_str     name
lenenc_str     org_name
lenenc_int     length of fixed-length fields [0c]2              
character set4              
column length1              
type2              
flags1              
decimals2              
filler [00] [00]  if command was COM_FIELD_LIST {
lenenc_int     
length of default-valuesstring[$len]   
default values
  }

更多详情 ： http://dev.mysql.com/doc/internals/en/com-query-response.html#column-definition

ColumnCount包类

/**
 * 
 * <pre><b>column definition command packet.</b></pre>
 * @author 
 * <pre>seaboat</pre>
 * <pre><b>email: </b>[e-mail]</pre>
 * <pre><b>blog: </b>http://www.php.cn/;/pre>
 * @version 1.0
 * @see http://www.php.cn/
 */public class ColumnDefinitionPacket extends MySQLPacket {
    private static final byte[] DEFAULT_CATALOG = "def".getBytes();    
    private static final byte NEXT_LENGTH = 0x0c;    
    private static final byte[] FILLER = { 00, 00 };    
    public byte[] catalog = DEFAULT_CATALOG;// always "def"
    public byte[] schema;    
    public byte[] table;    
    public byte[] orgTable;    
    public byte[] name;    
    public byte[] orgName;    
    public byte nextLength = NEXT_LENGTH;// always 0x0c
    public int charsetSet;    
    public long length;    
    public int type;    
    public int flags;    
    public byte decimals;    
    public byte[] filler = FILLER;    
    public byte[] defaultValues;    
    public void read(byte[] data) {
        MySQLMessage mm = new MySQLMessage(data);        
        this.packetLength = mm.readUB3();        
        this.packetId = mm.read();        
        this.catalog = mm.readBytesWithLength();        
        this.schema = mm.readBytesWithLength();        
        this.table = mm.readBytesWithLength();        
        this.orgTable = mm.readBytesWithLength();        
        this.name = mm.readBytesWithLength();        
        this.orgName = mm.readBytesWithLength();        
        this.nextLength = mm.read();        
        this.charsetSet = mm.readUB2();        
        this.length = mm.readUB4();        
        this.type = mm.read() & 0xff;        
        this.flags = mm.readUB2();        
        this.decimals = mm.read();        
        this.filler = mm.readBytes(2);        
        if (mm.hasRemaining()) {            
        this.defaultValues = mm.readBytesWithLength();
        }
    }    @Override
    public void write(ByteBuffer buffer) {        
    int size = calcPacketSize();
        BufferUtil.writeUB3(buffer, size);
        buffer.put(packetId);
        BufferUtil.writeWithLength(buffer, catalog, (byte) 0);
        BufferUtil.writeWithLength(buffer, schema, (byte) 0);
        BufferUtil.writeWithLength(buffer, table, (byte) 0);
        BufferUtil.writeWithLength(buffer, orgTable, (byte) 0);
        BufferUtil.writeWithLength(buffer, name, (byte) 0);
        BufferUtil.writeWithLength(buffer, orgName, (byte) 0);
        buffer.put(NEXT_LENGTH);
        BufferUtil.writeUB2(buffer, charsetSet);
        BufferUtil.writeUB4(buffer, length);
        buffer.put((byte) (type & 0xff));
        BufferUtil.writeUB2(buffer, flags);
        buffer.put(decimals);
        buffer.put(FILLER);        
        if (defaultValues != null) {            
        //only use for show columns
            BufferUtil.writeWithLength(buffer, defaultValues);
        }
    }    @Override
    public int calcPacketSize() {        
    int size = (catalog == null ? 1 : BufferUtil.getLength(catalog));
        size += (schema == null ? 1 : BufferUtil.getLength(schema));
        size += (table == null ? 1 : BufferUtil.getLength(table));
        size += (orgTable == null ? 1 : BufferUtil.getLength(orgTable));
        size += (name == null ? 1 : BufferUtil.getLength(name));
        size += (orgName == null ? 1 : BufferUtil.getLength(orgName));
        size += 13;        if (defaultValues != null) {
            size += BufferUtil.getLength(defaultValues);
        }        
        return size;
    }    
    @Override
    protected String getPacketInfo() {        
    return "MySQL Column Definition Packet";
    }

}

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