java在文件中写入数据
我发现了这个如何从PostgreSQL读取二进制文件的示例
conn.setAutoCommit(false);
// Get the Large Object Manager to perform operations with
LargeObjectManager lobj = ((org.postgresql.PGConnection) conn).getLargeObjectAPI();
ps = conn.prepareStatement("SELECT FILE FROM KNOWLEDGEBASE_FILES WHERE ID = ?");
ps.setInt(1, 333);
ResultSet rs = ps.executeQuery();
while (rs.next())
{
// Open the large object for reading
long oid = rs.getLong(1);
LargeObject obj = lobj.open(oid, LargeObjectManager.READ);
// Read the data
byte buf[] = new byte[obj.size()];
obj.read(buf, 0, obj.size());
// Do something with the data read here
FileChannel rwChannel = new RandomAccessFile("License_Agreement.pdf", "rw").getChannel();
ByteBuffer wrBuf = rwChannel.map(FileChannel.MapMode.READ_WRITE, 0, buffer.length * number_of_lines);
for (int i = 0; i < obj.size(); i++)
{
wrBuf.put(obj);
}
// Close the object
obj.close();
}
rs.close();
ps.close();
// Finally, commit the transaction.
conn.commit();
如何使用NIO将数据写入文件
在这一行wrBuf.put(obj);
我得到一个错误:
找不到适合put的方法(大对象) 方法:比特布弗法。put(字节)不适用 (参数不匹配;无法将LargeObject转换为字节) 方法:比特布弗法。put(ByteBuffer)不适用 (参数不匹配;无法将LargeObject转换为ByteBuffer) 方法:比特布弗法。put(字节[])不适用 (参数不匹配;无法将LargeObject转换为字节[])
# 1 楼答案
你可以使用LargeObject::getInputStream: