利用JDBC操作Oracle CLOB和BLOB类型数据

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对LOB数据（包括CLOB BLOB NCLOB BFILE类型）操作的插入操作步骤：插入空值-->获取空值列及更新锁-->更新LOB字段。

通过查询操作得到的LOB类型数据处理要点：首先利用LOB字段数据获取InputStream或OutputStream对象，然后根据需要对其进行操作，若需提取数据则获取InputStream对象，若需更新LOB字段数据，则获取OutputStream对象。

程序分为两层，1)JdbcUtil提供基本数据库访问及事务管理，2)DAO层调用JdbcUtil来提供DAO服务。

包含CLOB数据的content_text表：

/*==============================================================*/
/* Table: content_text                                        */
/*==============================================================*/
CREATE TABLE content_text  (
   pk_content_text    INTEGER                         NOT null,
   text_type          VARCHAR2(25)                    NOT null,
   text_content       CLOB                            NOT null,
   CONSTRAINT PK_CONTENT_TEXT PRIMARY KEY (pk_content_text)
)

包含BLOB数据的content_bin表：

/*==============================================================*/
/* Table: content_bin                                         */
/*==============================================================*/
CREATE TABLE content_bin  (
   pk_content_bin     INTEGER                         NOT null,
   bin_type           VARCHAR2(25)                    NOT null,
   bin_content        CLOB                            NOT null,
   CONSTRAINT PK_CONTENT_BIN PRIMARY KEY (pk_content_bin)
);

=========================JdbcUtil================
-------向content_text表中插入数据：

public int insertText(ContentText text) {
		int insertkey = -1;
		try {
			// 利用序列sequence向数据库索取content_text表的自增长主键
			ResultSet rs = executeQuery("select seq_content_text.nextval as pk_content_text from dual");
			rs.first();
			insertkey = rs.getInt(1);
			rs.close();

			// 插入空CLOB
			String insertEmpty = "insert into content_text values(" + insertkey
					+ ",'" + text.getTextType() + "',empty_clob())";
			boolean insertResult = executeUpdate(insertEmpty);
			if (insertResult == false) {
				throw new SQLException();
			}

			// 获取CLOB类型列text_content，并获取更新锁，锁定当前行直至更新结束
			String getForUpdate = "select text_content from content_text where pk_content_text = "
					+ insertkey + " for update";
			rs = executeQuery(getForUpdate);
			rs.first();
			CLOB content = (CLOB) rs.getClob("text_content");
			rs.close();
			content.setString(1L, text.getContent());

			// 更新text_content列
			String updateSQL = "update content_text set text_content = ? where pk_content_text = ?";
			PreparedStatement pst = conn.prepareStatement(updateSQL);
			pst.setClob(1, content);
			pst.setInt(2, insertkey);
			pst.execute();
			pst.close();
		} catch (SQLException e) {
			try {
				conn.rollback();
				conn.close();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
			e.printStackTrace();
			System.out.println("Insert text failed!");
		}
		return insertkey;
	}

------------向content_bin表中插入数据：

public int insertBin(ContentBin bin) {
		int insertkey = -1;
		try {
			// 利用序列sequence向数据库索取content_bin表的自增长主键
			ResultSet rs = executeQuery("select seq_content_bin.nextval from dual");
			boolean good = rs.first();
			System.out.println(good);
			insertkey = rs.getInt(1);
			rs.close();

			// 插入空BLOB
			String insertEmpty = "insert into content_bin values(" + insertkey
					+ ",'" + bin.getBinType() + "','" + bin.getBinFilename()
					+ "',empty_blob())";
			boolean result = executeUpdate(insertEmpty);
			System.out.println("插入空值：" + result);

			// 获取空BLOB字段，并获取更新锁
			String getEmpty = "select bin_content from content_bin where pk_content_bin="
					+ insertkey + " for update";
			ResultSet forupdateRs = executeQuery(getEmpty);
			forupdateRs.first();
			BLOB blob = (BLOB) forupdateRs.getBlob(1);
			
			//由文件系统获取文件输入流
			File file = bin.getContent();
			System.out.println(file.getAbsolutePath());
			FileInputStream fin = new FileInputStream(file);
			System.out.println(fin.toString());
			
			// 获取BLOB的输出流，并从文件输入流获取数据，写入BLOB的输出流，完成数据库外的BLOB更新
			OutputStream out = blob.setBinaryStream(0);
			byte[] data = new byte[blob.getBufferSize()];
			System.out.println(data.length);
			int count = -1, total = 0;
			while ((count = fin.read(data)) != -1) {
				total += count;
				out.write(data, 0, count);
			}
			fin.close();
			out.close();

			// 利用新的BLOB更新数据库
			String updateBin = "update content_bin set bin_content=? where pk_content_bin=?";
			PreparedStatement pstmt = conn.prepareStatement(updateBin);
			pstmt.setBlob(1, blob);
			pstmt.setInt(2, insertkey);
			pstmt.execute();
			pstmt.close();

		} catch (SQLException e) {
			try {
				conn.rollback();
				conn.close();
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return insertkey;
	}

=============================DAO层====================
---------查询content_text表

public ContentText getById(int id) {
		jdbc.openConn();
		ContentText text = new ContentText();
		String sql = "select pk_content_text,text_type,text_content from content_text where pk_content_text = "
				+ id;
		ResultSet rs = jdbc.executeQuery(sql);
		try {
			rs.first();
			text.setContentId(rs.getInt("pk_content_text"));
			text.setTextType(rs.getString("text_type"));
			CLOB clob = (CLOB) rs.getClob(3);
			char[] chars = new char[(int) clob.getLength()];//(int)clob.length();
			clob.getCharacterStream().read(chars);
			String content = new String(chars);
			text.setContent(content);
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		jdbc.commitAndCloseConn();
		return text;
	}

--------------查询content_bin表

public ContentBin getById(int id) {
		ContentBin bin = new ContentBin();
		jdbc.openConn();
		String sql = "select pk_content_bin,bin_type,bin_filename,bin_content from content_bin where pk_content_bin="+ id;
		ResultSet rs = jdbc.executeQuery(sql);
		try {
			rs.first();
			bin.setContentId(rs.getInt(1));
			bin.setBinType(rs.getString(2));
			String filename = rs.getString(3);
			bin.setBinFilename(filename);
			//利用字段bin_filename值构造文件
			File file = new File(filename);
			FileOutputStream sout = new FileOutputStream(file);
			BLOB blob = (BLOB) rs.getBlob(4);
			InputStream in = blob.getBinaryStream();//获取BLOB数据的输入数据流
			//经BLOB输入数据流读取数据，并将其写入文件
			byte[] b = new byte[256]; 
			int off = 0;
			int len = b.length;
			for (int i = in.read(b); i != -1;) { 
				sout.write(b); 
				System.out.println(i);
				i = in.read(b);
			} 
			in.close();
			sout.close();
			bin.setContent(file);
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		jdbc.commitAndCloseConn();
		return bin;
	}