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MySQL and Oracle processing CLOB and blob fields
2022-06-25 11:04:00 【Anonymous & Xiaoyu】
MySQL and Oracle In the face of Clob and Blob Field processing
List of articles
Preface
One 、MySQL And Oracle How the database handles Clob,Blob data type
(1) Not corresponding in the database clob,blob Of the following types ：
MySQL in ：clob Corresponding text,blob Corresponding blob
DB2/Oracle in ：clob Corresponding clob,blob Corresponding blob
(2) domain The corresponding type in ：
clob Corresponding String,blob Corresponding byte[]
clob Corresponding java.sql.Clob,blob Corresponding java.sql.Blob
(3) hibernate The corresponding type in the configuration file ：
clob–>clob ,blob–>binary
You can also directly use the database to provide types , for example ：oracle.sql.Clob,oracle.sql.Blob
Two 、jdbc operation clob( With oracle For example )
1. The insert
First operate clob/blob Unlike operation varchar The type is as simple , The insertion step is generally divided into two steps ： The first step is to insert a null value , The second step is to lock the trip , to update clob/blob Field .
// Insert a null value
conn.setAutoCommit(false);
String sql = "INSERT INTO T_FILE(NAME, FILE_CONTENT) VALUES ('Jambhala', EMPTY_CLOB())";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.executeUpdate();
// Lock this trip
String sql_lockstr = "SELECT FILE_CONTENT FROM T_FILE WHERE NAME='Jambhala' FOR UPDATE";
pstmt = conn.prepareStatement(sql_lockstr);
ResultSet rs = pstmt.executeQuery();
oracle.sql.Clob clob = (oracle.sql.Clob)rs.getClob(1);
java.io.OutputStream writer = clob.getAsciiOutputStream();
byte[] temp = newFileContent.getBytes();
writer.write(temp);
writer.flush();
writer.close();
pstmt.close();
2. Read operation
The code is as follows （ Example ）：
oracle.sql.Clob clob = rs.getClob("FILE_CONTENT");
if(clob != null){
Reader is = clob.getCharacterStream();
BufferedReader br = new BufferedReader(is);
String s = br.readLine();
while(s != null){
content += s+"<br>";
s = br.readLine();
}
}
3、 ... and 、jdbc operation blob
conn.setAutoCommit(false);
String sql = "INSERT INTO T_PHOTO(NAME, PHOTO) VALUES ('Jambhala', EMPTY_BLOB())";
pstmt = conn.prepareStatement(sql);
pstmt = conn.executeUpdate();
sql = "SELECT PHOTO FROM T_PHOTO WHERE NAME='Jambhala'";
pstmt = conn.prepareStatement(sql);
rs = pstmt.executeQuery(sql);
if(rs.next()){
oracle.sql.Blob blob = (oracle.sql.Blob)rs.getBlob(1);
}
//write to a file
File file=new File("C:\\test.rar");
FileInputStream fin = new FileInputStream(file);
OutputStream out = blob.getBinaryOutputStream();
int count=-1,total=0;
byte[] data = new byte[blob.getBufferSize()];
while((count=fin.read(data)) != -1){
total += count;
out.write(data, 0, count);
}
Four 、hibernate Handle clob
MyFile file = new MyFile();
file.setName("Jambhala");
file.setContent(Hibernate.createClob(""));
session.save(file);
session.flush();
session.refresh(file, LockMode.UPGRADE);
oracle.sql.Clob clob = (oracle.sql.Clob)file.getContent();
Writer pw = clob.getCharacterOutputStream();
pw.write(longText); // Write long text
pw.close();
session.close();
5、 ... and 、 Use hibernate Handle blob
The principle is basically the same ：
Photo photo = new Photo();
photo.setName("Jambhala");
photo.setPhoto(Hibernate.createBlob(""));
session.save(photo);
session.flush();
session.refresh(photo, LockMode.UPGRADE); // Lock this object
oracle.sql.Blob blob = photo.getPhoto(); // Get this blob The pointer to
OutputStream out = blob.getBinaryOutputStream();
// Write a file
File f = new File("C:\\test.rar");
FileInputStream fin = new FileInputStream(f);
int count=-1,total=0;
byte[] data = new byte[(int)fin.available()];
out.write(data);
fin.close();
out.close();
session.flush();
String DRIVER = "oracle.jdbc.driver.OracleDriver";
//Oracle For connection URL
private static final String URL = "jdbc:oracle:thin:@testora:1521:orac";
// user name
private static final String USER = "scott";
// password
private static final String PASSWORD = "pswd";
// Database connection
private static Connection conn = null;
//SQL Statement object
private static Statement stmt = null;
//@roseuid 3EDA089E02BC
public LobPros(){
}
// Insert a new... Into the database Clob object
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA089E02BC
public static void clobInsert(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try{
// Insert an empty Clob object
stmt.executeUpdate("INSERT INTO TEST_CLOB VALUES ('111', EMPTY_CLOB())");
// Query the Clob Object and lock
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");
while(rs.next()){
// Remove this Clob object
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
// towards Clob Object
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while((c=in.read()) != -1){
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
}catch(Exception e){
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// modify Clob object ( It's in the original Clob Based on the object )
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA089E02BC
public static void clobModify(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try{
// Inquire about Clob Object and lock
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");
while(rs.next()){
// Access to this Clob object
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
// Make overwriting changes
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
}catch(Exception e){
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// Replace CLOB object （ The original CLOB Object cleanup , Replace it with a brand new one CLOB object
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA04BF01E1
public static void clobReplace(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try{
// Empty original CLOB object
stmt.executeUpdate("UPDATE TEST_CLOB SET CLOBCOL=EMPTY_CLOB() WHERE ID='111'");
// Inquire about CLOB Object and lock
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");
while (rs.next()) {
// Access to this CLOB object
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
// Update data
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
}catch(Exception e){
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
//CLOB Object read
//@param outfile Output file name
//@throws java.lang.Exception
//@roseuid 3EDA04D80116
public static void clobRead(String outfile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try{
// Inquire about CLOB object
ResultSet rs = stmt.executeQuery("SELECT * FROM TEST_CLOB WHERE ID='111'");
while (rs.next()) {
// obtain CLOB object
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
// Output in character form
BufferedReader in = new BufferedReader(clob.getCharacterStream());
BufferedWriter out = new BufferedWriter(new FileWriter(outfile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
out.close();
in.close();
}
}catch(Exception e){
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// Insert a new... Into the database BLOB object
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA04E300F6
public static void blobInsert(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
// Insert an empty BLOB object
stmt.executeUpdate("INSERT INTO TEST_BLOB VALUES ('222', EMPTY_BLOB())");
// Query the BLOB Object and lock
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");
while (rs.next()) {
// Remove this BLOB object
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
// towards BLOB Object
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
} catch (Exception e) {
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// modify BLOB object （ It's in the original BLOB Based on the object ）
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA04E90106
public static void blobModify(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
// Inquire about BLOB Object and lock
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");
while (rs.next()) {
// Remove this BLOB object
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
// towards BLOB Object
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
} catch (Exception e) {
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// Replace BLOB object （ The original BLOB Object cleanup , Replace it with a brand new one BLOB object ）
//@param infile Data files
//@throws java.lang.Exception
//@roseuid 3EDA0505000C
public static void blobReplace(String infile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
// Empty original BLOB object
stmt.executeUpdate("UPDATE TEST_BLOB SET BLOBCOL=EMPTY_BLOB() WHERE ID='222'");
// Query the BLOB Object and lock
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");
while (rs.next()) {
// Remove this BLOB object
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
// towards BLOB Object
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
} catch (Exception e) {
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
//BLOB Object read
//@param outfile Output file name
//@throws java.lang.Exception
//@roseuid 3EDA050B003B
public static void blobRead(String outfile) throws Exception {
// Set not to submit automatically
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
// Inquire about BLOB object
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222'");
while (rs.next()) {
// Remove this BLOB object
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
// Output in binary form
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outfile));
BufferedInputStream in = new BufferedInputStream(blob.getBinaryStream());
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
// Formal submission
conn.commit();
} catch (Exception e) {
// Error rollback
conn.rollback();
throw e;
}
// Restore the original submission status
conn.setAutoCommit(defaultCommit);
}
// Create test forms
//@throws Exception
public static void createTables() throws Exception {
try {
stmt.executeUpdate("CREATE TABLE TEST_CLOB (ID NUMBER(3), CLOBCOL CLOB)");
stmt.executeUpdate("CREATE TABLE TEST_BLOB (ID NUMBER(3), BLOBCOL BLOB)");
} catch (Exception e) {
}
}
//@param args - Command line arguments
//@throws java.lang.Exception
//@roseuid 3EDA052002AC
public static void main(String[] args) throws Exception {
// Loading drive , Establish a database connection
Class.forName(DRIVER);
conn = DriverManager.getConnection(URL,USER,PASSWORD);
stmt = conn.createStatement();
// Set up test forms
createTables();
//CLOB Object insertion test
clobInsert("c:/clobInsert.txt");
clobRead("c:/clobInsert.out");
//CLOB Object modification test
clobModify("c:/clobModify.txt");
clobRead("c:/clobModify.out");
//CLOB Object replacement test
clobReplace("c:/clobReplace.txt");
clobRead("c:/clobReplace.out");
//BLOB Object insertion test
blobInsert("c:/blobInsert.doc");
blobRead("c:/blobInsert.out");
//BLOB Object modification test
blobModify("c:/blobModify.doc");
blobRead("c:/blobModify.out");
//BLOB Object replacement test
blobReplace("c:/blobReplace.doc");
blobRead("c:/bolbReplace.out");
// Close resource exit
conn.close();
System.exit(0);
}
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