JDBC:LOB---BLOB、CLOB
Oracle LOB
将数据以字节流的形式存储在数据库的内部。因而，内部 LOB 的许多操作都可以参与事务，也可以像处理普通数据一样对其进行备份和恢复操作。
Oracle 支持三种类型的内部 LOB ：
MySQL BLOB
•MySQ L 的四种 BLOB 类型 ( 除了在存储的最大信息量上不同外，他们是等同的 )
需要注意的是：如果存储的文件过大，数据库的性能会下降。
JDBC读写BLOB
/**
* 读取 blob 数据:
* 1. 使用 getBlob 方法读取到 Blob 对象
* 2. 调用 Blob 的 getBinaryStream() 方法得到输入流。再使用 IO 操作即可.
*/
@Test
public void readBlob(){
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = JDBCTools.getConnection();
String sql = "SELECT id, name customerName, email, birth, picture "
+ "FROM customers WHERE id = 13";
preparedStatement = connection.prepareStatement(sql);
resultSet = preparedStatement.executeQuery();
if(resultSet.next()){
int id = resultSet.getInt(1);
String name = resultSet.getString(2);
String email = resultSet.getString(3);
System.out.println(id + ", " + name + ", " + email);
Blob picture = resultSet.getBlob(5);
InputStream in = picture.getBinaryStream();
System.out.println(in.available());
OutputStream out = new FileOutputStream("flower.jpg");
byte [] buffer = new byte[1024];
int len = 0;
while((len = in.read(buffer)) != -1){
out.write(buffer, 0, len);
}
in.close();
out.close();
}
} catch (Exception e) {
e.printStackTrace();
} finally{
JDBCTools.releaseDB(resultSet, preparedStatement, connection);
}
}
/**
* 插入 BLOB 类型的数据必须使用 PreparedStatement：因为 BLOB 类型
* 的数据时无法使用字符串拼写的。
*
* 调用 setBlob(int index, InputStream inputStream)
*/
@Test
public void testInsertBlob(){
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
connection = JDBCTools.getConnection();
String sql = "INSERT INTO customers(name, email, birth, picture)"
+ "VALUES(?,?,?,?)";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, "ABCDE");
preparedStatement.setString(2, "[email protected]");
preparedStatement.setDate(3,
new Date(new java.util.Date().getTime()));
InputStream inputStream = new FileInputStream("Hydrangeas.jpg");
preparedStatement.setBlob(4, inputStream);
preparedStatement.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
} finally{
JDBCTools.releaseDB(null, preparedStatement, connection);
}
}
获取图片二进制再缩放
public class OracleQueryBean {
private final String oracleDriverName = "oracle.jdbc.driver.OracleDriver";
private Connection myConnection = null;
/*图片表名*/
private String strTabName;
/*图片ID字段名*/
private String strIDName;
/*图片字段名*/
private String strImgName;
/**
* 加载java连接Oracle的jdbc驱动
*/
public OracleQueryBean(){
try{
Class.forName(oracleDriverName);
}catch(ClassNotFoundException ex){
System.out.println("加载jdbc驱动失败,原因:" + ex.getMessage());
}
}
/**
* 获取Oracle连接对象
* @return Connection
*/
public Connection getConnection(){
try{
//用户名+密码; 以下使用的Test就是Oracle里的表空间
//从配置文件中读取数据库信息
GetPara oGetPara = new GetPara();
String strIP = oGetPara.getPara("serverip");
String strPort = oGetPara.getPara("port");
String strDBName = oGetPara.getPara("dbname");
String strUser = oGetPara.getPara("user");
String strPassword = oGetPara.getPara("password");
this.strTabName = oGetPara.getPara("tablename");
this.strIDName = oGetPara.getPara("imgidname");
this.strImgName = oGetPara.getPara("imgname");
String oracleUrlToConnect ="jdbc:oracle:thin:@"+strIP+":"+strPort+":"+strDBName;
this.myConnection = DriverManager.getConnection(oracleUrlToConnect, strUser, strPassword);
}catch(Exception ex){
System.out.println("Can not get connection:" + ex.getMessage());
System.out.println("请检测配置文件中的数据库信息是否正确." );
}
return this.myConnection;
}
/**
* 根据图片在数据库中的ID进行读取
* @param strID 图片字段ID
* @param w 需要缩到的宽度
* @param h 需要缩到高度
* @return 缩放后的图片的byte数据
*/
public byte[] GetImgByteById(String strID, int w, int h){
//System.out.println("Get img data which id is " + nID);
if(myConnection == null)
this.getConnection();
byte[] data = null;
try {
Statement stmt = myConnection.createStatement();
ResultSet myResultSet = stmt.executeQuery("select " + this.strIDName + " from " + this.strTabName + " where " + this.strIDName + "=" + strID);
StringBuffer myStringBuffer = new StringBuffer();
if (myResultSet.next()) {
java.sql.Blob blob = myResultSet.getBlob(this.strImgName);
InputStream inStream = blob.getBinaryStream();
try {
long nLen = blob.length();
int nSize = (int) nLen;
//System.out.println("img data size is :" + nSize);
data = new byte[nSize];
inStream.read(data);
inStream.close();
} catch (IOException e) {
System.out.println("获取图片数据失败,原因:" + e.getMessage());
}
data = ChangeImgSize(data, w, h);
}
System.out.println(myStringBuffer.toString());
myConnection.commit();
myConnection.close();
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
return data;
}
/**
* 根据图片在数据库中的ID进行读取，显示原始大小的图片
* @param strID 图片字段ID
* @return 读取后的图片byte数据
*/
public byte[] GetImgByteById(String strID){
//System.out.println("Get img data which id is " + nID);
if(myConnection == null)
this.getConnection();
byte[] data = null;
try {
Statement stmt = myConnection.createStatement();
ResultSet myResultSet = stmt.executeQuery("select " + this.strIDName + " from " + this.strTabName + " where " + this.strIDName + "=" + strID);
StringBuffer myStringBuffer = new StringBuffer();
if (myResultSet.next()) {
java.sql.Blob blob = myResultSet.getBlob(this.strImgName);
InputStream inStream = blob.getBinaryStream();
try {
long nLen = blob.length();
int nSize = (int) nLen;
data = new byte[nSize];
inStream.read(data);
inStream.close();
} catch (IOException e) {
System.out.println("获取图片数据失败,原因:" + e.getMessage());
}
}
System.out.println(myStringBuffer.toString());
myConnection.commit();
myConnection.close();
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
return data;
}
/**
* 缩小或放大图片
* @param data 图片的byte数据
* @param w 需要缩到的宽度
* @param h 需要缩到高度
* @return
*/
private byte[] ChangeImgSize(byte[] data, int nw, int nh){
byte[] newdata = null;
try{
BufferedImage bis = ImageIO.read(new ByteArrayInputStream(data));
int w = bis.getWidth();
int h = bis.getHeight();
double sx = (double) nw / w;
double sy = (double) nh / h;
AffineTransform transform = new AffineTransform();
transform.setToScale(sx, sy);
AffineTransformOp ato = new AffineTransformOp(transform, null);
//原始颜色
BufferedImage bid = new BufferedImage(nw, nh, BufferedImage.TYPE_3BYTE_BGR);
ato.filter(bis, bid);
//转换成byte字节
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bid, "jpeg", baos);
newdata = baos.toByteArray();
}catch(IOException e){
e.printStackTrace();
}
return newdata;
}
}