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weblogic服务器中,在通过datasourse获取connection,BLOB字段取出来的就不是oracle.sql.BLOB类型,而是weblogic封装过的OracleThinBlob类型,执行BLOB oBLOB = (BLOB) rs.getBlob(1);所以cast的时候肯定会出错,出现ClassCaseException异常。
一,在使用JDBC直接连接的时候(代码引用dev2dev.bea.com.cn)
详细参见:http://dev2dev.bea.com.cn/bbsdoc/20050971.html#_Toc94603600
java 代码
- java.sql.Blob myBlob= null;
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- java.sql.Clob myClob= null;
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- Connection conn = null;
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- Properties props = new Properties();
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- props.put("user",user);
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- props.put("password", password);
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- props.put("server",server);
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- Driver myDriver = (Driver)
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- Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
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- conn = myDriver.connect("jdbc:oracle:thin:" , props);
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- Statement crstmt = conn.createStatement();
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- crstmt.execute("create table lobtest (id int, blobcol Blob, clobcol Clob)");//建表
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- stmt.execute("insert into lobtest values (44,EMPTY_BLOB(),EMPTY_CLOB())");//插入数据
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- stmt.execute("select * from lobtest where id=44");//取数据
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- ResultSet rs = stmt.getResultSet();
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- while ( rs.next() ) {
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- myBlob = rs.getBlob("blobcol");
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- }
-
-
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- // Create a byte array and store some data in it
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- System.out.println("\nCreating the following byte array:");
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- int STREAM_SIZE = 10;
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- byte[] b = new byte[STREAM_SIZE];
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- for (int i=0; i < STREAM_SIZE; i++) {
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- b = (byte)(40 + (i%20)); // range 40-60
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- System.out.println("byte[" + i + "] = " + b);
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- }
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-
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- // Write the byte array to a stream and store it in the Blob column
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- System.out.println
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- ("\nWriting the byte array to a stream" +
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- " and storing it in the table as a blob...");
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- InputStream is = new ByteArrayInputStream(b);
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- OutputStream os = ((oracle.sql.BLOB) myBlob).getBinaryOutputStream();
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- byte[] inBytes = new byte[STREAM_SIZE];
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- int numBytes = is.read(inBytes);
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-
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- // write the input stream to the output stream
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- while (numBytes > 0) {
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- os.write(inBytes, 0, numBytes);
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- numBytes = is.read(inBytes);
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- }
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- // The flush() method causes the data to be written to the table
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- os.flush();
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-
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- //read back the blob
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- System.out.println("\nReading the blob back from the table and displaying:");
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- Statement readblob = conn.createStatement();
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- readblob.execute("select * from lobtest where id=44");
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- ResultSet rsreadblob = readblob.getResultSet();
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-
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- // read the blob into a byte array and display
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- byte[] r = new byte[STREAM_SIZE];
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- while ( rsreadblob.next() ) {
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- Blob myReadBlob =rsreadblob.getBlob("blobcol");
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- java.io.InputStream readis = myReadBlob.getBinaryStream();
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- for (int i=0 ; i < STREAM_SIZE ; i++) {
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- r = (byte) readis.read();
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- System.out.println("output [" + i + "] = " + r);
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- }
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- }
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-
-
-
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- // create some character data to work with
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- String ss = "abcdefghijklmnopqrstuvwxyz";
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- System.out.println("\nCreated the following string to be stored as a clob:\n" +
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- ss);
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- // ============== Manipulating the Clob column ======================
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- // get a reference to the clob column
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- stmt.execute("select * from lobtest where id=44");
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- ResultSet crs = stmt.getResultSet();
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- while ( crs.next() ) {
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- myClob = crs.getClob("clobcol");
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- java.io.OutputStream osss =
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- ((oracle.sql.CLOB) myClob).getAsciiOutputStream();
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- byte[] bss = ss.getBytes("ASCII");
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- osss.write(bss);
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- osss.flush();
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- }
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- conn.commit();
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- // read back the clob
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- System.out.println("\nReading the clob back from the table and displaying:");
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- Statement readclob = conn.createStatement();
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- readclob.execute("select * from lobtest where id=44");
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- ResultSet rsreadclob = readclob.getResultSet();
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- // read the clob in as and ASCII stream, write to a character array, and display
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- while ( rsreadclob.next() ) {
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- Clob myReadClob =rsreadclob.getClob("clobcol");
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- java.io.InputStream readClobis = myReadClob.getAsciiStream();
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- char[] c = new char[26];
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- for (int i=0 ; i < 26; i++) {
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- c = (char) readClobis.read();
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- System.out.println("output [" + i + "] = " + c);
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- }
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- }
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- // Drop the table and clean up connections
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- System.out.println("\nDropping table...");
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- Statement dropstmt = conn.createStatement();
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- dropstmt.execute("drop table lobtest");
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- System.out.println("Table dropped.");
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- } catch (Exception e) {
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- System.out.println("Exception was thrown: " + e.getMessage());
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- throw e;
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- } finally {
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- try {
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- if (conn != null)
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- conn.close();
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- } catch (SQLException sqle) {
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- System.out.println("SQLException was thrown: " + sqle.getMessage());
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- throw sqle;
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- }
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- }
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- }
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二,使用数据源的情况,并且使用oracle thin驱动方式
为了使代码适应各种应用服务器,可以对代码这样修改
- 在weblogic中找到这个jar包加入到工程项目中。weblogic.jar
- 在处理BLOB字段的类中添加引用import weblogic.jdbc.vendor.oracle.OracleThinBlob;
- 取得BLOB字段的时候原来的处理方式是BLOB oBLOB = (BLOB) rs.getBlob(j + 1);这里的BLOB是 oracle.sql.BLOB。在weblogic服务器下这样使用就会报ClassCaseException,因为在强制类型转换的时候,rs.getBlob(j + 1)得到的是OracleThinBlob类型。所以代码更改为
java 代码
- if(rs.getBlob(j + 1).getClass().equals(oracle.sql.BLOB.class)) {//except weblogic
- BLOB oBLOB = (BLOB) rs.getBlob(j + 1);
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- }else{//for weblogic
- OracleThinBlob oBLOB = (OracleThinBlob) rs.getBlob(j + 1);
附录:引用自javaeye JAVA完全控制Oracle中BLOB CLOB说明
----------厚厚发表于 2006年06月27日
网络上很多关于JAVA对Oracle中BLOB、CLOB类型字段的操作说明,有的不够全面,有的不够准确,甚至有的简直就是胡说八道。最近的项目正巧用到了这方面的知识,在这里做个总结。
环境:
Database: Oracle 9i
App Server: BEA Weblogic 8.14
表结构:
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), BLOBATTR Blob)
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), CLOBATTR Clob)
JAVA可以通过JDBC,也可以通过JNDI访问并操作数据库,这两种方式的具体操作存在着一些差异,由于通过App Server的数据库连接池JNDI获得的数据库连接提供的java.sql.Blob和java.sql.Clob实现类与JDBC方式提供的不同,因此在入库操作的时候需要分别对待;出库操作没有这种差异,因此不用单独对待。
一、BLOB操作
1、入库
(1)JDBC方式
//通过JDBC获得数据库连接
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:testdb", "test", "test");
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_blob()
st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
//锁定数据行进行更新,注意“for update”语句
ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Blob对象后强制转换为oracle.sql.BLOB
oracle.sql.BLOB blob = (oracle.sql.BLOB) rs.getBlob("BLOBATTR");
OutputStream outStream = blob.getBinaryOutputStream();
//data是传入的byte数组,定义:byte[] data
outStream.write(data, 0, data.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
(2)JNDI方式
//通过JNDI获得数据库连接
Context context = new InitialContext();
ds = (DataSource) context.lookup("ORA_JNDI");
Connection con = ds.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_blob()
st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
//锁定数据行进行更新,注意“for update”语句
ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Blob对象后强制转换为weblogic.jdbc.vendor.oracle.OracleThinBlob(不同的App Server对应的可能会不同)
weblogic.jdbc.vendor.oracle.OracleThinBlob blob = (weblogic.jdbc.vendor.oracle.OracleThinBlob) rs.getBlob("BLOBATTR");
OutputStream outStream = blob.getBinaryOutputStream();
//data是传入的byte数组,定义:byte[] data
outStream.write(data, 0, data.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
2、出库
//获得数据库连接
Connection con = ConnectionFactory.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//不需要“for update”
ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1");
if (rs.next())
{
java.sql.Blob blob = rs.getBlob("BLOBATTR");
InputStream inStream = blob.getBinaryStream();
//data是读出并需要返回的数据,类型是byte[]
data = new byte[input.available()];
inStream.read(data);
inStream.close();
}
inStream.close();
con.commit();
con.close();
二、CLOB操作
1、入库
(1)JDBC方式
//通过JDBC获得数据库连接
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:testdb", "test", "test");
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_clob()
st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
//锁定数据行进行更新,注意“for update”语句
ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Clob对象后强制转换为oracle.sql.CLOB
oracle.sql.CLOB clob = (oracle.sql.CLOB) rs.getClob("CLOBATTR");
Writer outStream = clob.getCharacterOutputStream();
//data是传入的字符串,定义:String data
char[] c = data.toCharArray();
outStream.write(c, 0, c.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
(2)JNDI方式
//通过JNDI获得数据库连接
Context context = new InitialContext();
ds = (DataSource) context.lookup("ORA_JNDI");
Connection con = ds.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_clob()
st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
//锁定数据行进行更新,注意“for update”语句
ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Clob对象后强制转换为weblogic.jdbc.vendor.oracle.OracleThinClob(不同的App Server对应的可能会不同)
weblogic.jdbc.vendor.oracle.OracleThinClob clob = (weblogic.jdbc.vendor.oracle.OracleThinClob) rs.getClob("CLOBATTR");
Writer outStream = clob.getCharacterOutputStream();
//data是传入的字符串,定义:String data
char[] c = data.toCharArray();
outStream.write(c, 0, c.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
2、出库
//获得数据库连接
Connection con = ConnectionFactory.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//不需要“for update”
ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1");
if (rs.next())
{
java.sql.Clob clob = rs.getClob("CLOBATTR");
Reader inStream = clob.getCharacterStream();
char[] c = new char[(int) clob.length()];
inStream.read(c);
//data是读出并需要返回的数据,类型是String
data = new String(c);
inStream.close();
}
inStream.close();
con.commit();
con.close();
需要注意的地方:
1、java.sql.Blob、oracle.sql.BLOB、weblogic.jdbc.vendor.oracle.OracleThinBlob几种类型的区别
2、java.sql.Clob、oracle.sql.CLOB、weblogic.jdbc.vendor.oracle.OracleThinClob几种类型的区别 |
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