JDBC 对oracle 的clob ，blob类型的操作方式

感谢：http://idealab.javaeye.com/blog/383409

利用JDBC操作Oracle CLOB和BLOB类型数据

关键字: jdbc oracle clob blob
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：

Sql代码

/*==============================================================*/

/* 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：

Sql代码

/*==============================================================*/

/* 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：

Java代码

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：

Java代码

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

Java代码

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

Java代码

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;

}