【深入Hibernate】——根据业务自定义Clob数据类型

  引言

 

  最近项目涉及到大文本字段Clob，它是大文本中多字节存储数据类型，还有一个与它类似的是Blob，Blob是大文

本单字节存储数据类型。看《深入浅出Hibernate》里看到Clob可以进行自定义数据类型，很受用，所以这里将代码

留存下来备用。

  代码

  public class StringClobType implements UserType {

private static final String ORACLE_DRIVER_NAME="Oracle JDBC driver";
private static final int ORACLE_DRIVER_MAJOR_VERSION=9;
private static final int ORACLE_DRIVER_MINOR_VERSION=0;

@Override
public int[] sqlTypes() {
return new int[]{Types.CLOB};
}

@Override
public Class returnedClass() {
return String.class;
}

@Override
public boolean equals(Object x, Object y) throws HibernateException {
return !org.apache.commons.lang3.ObjectUtils.notEqual(x,y);
}

@Override
public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {
Clob clob = rs.getClob(names[0]);
return (
clob == null?null:clob.getSubString(1,(int)clob.length()));
}

@Override
public void nullSafeSet(PreparedStatement st, Object value, int index) throws HibernateException, SQLException {
DatabaseMetaData dbMetaData = st.getConnection().getMetaData();
if(value == null){
st.setNull(index,sqlTypes()[0]);
}else if (ORACLE_DRIVER_NAME.equals(dbMetaData.getDriverName())){
if(dbMetaData.getDriverMajorVersion() >= ORACLE_DRIVER_MAJOR_VERSION &&
dbMetaData.getDriverMinorVersion() >= ORACLE_DRIVER_MINOR_VERSION){

try{
Class oracleClobClass = Class.forName("oracle.sql.CLOB");
Class partypes[] = new Class[3];
partypes[0] = Connection.class;
partypes[1] = Boolean.TYPE;
partypes[2] = Integer.TYPE;
Method createTemporaryMethod = oracleClobClass.getDeclaredMethod("createTemporary",partypes);
Field durationSessionField = oracleClobClass.getField("DURATION_SESSION");
Object arglist[] = new Object[3];
Connection conn = st.getConnection().getMetaData().getConnection();

Class oracleConnectionClass=Class.forName("oracle.jdbc.OracleConnection");
if(!oracleClobClass.isAssignableFrom(conn.getClass())){
throw new HibernateException("Must be a oracle.jdbc.OracleConnection",conn.getClass().getName());
}

arglist[0] = conn;
arglist[1] = Boolean.TYPE;
arglist[2] = durationSessionField.get(null);

Object tempClob = createTemporaryMethod.invoke(null,arglist);
partypes = new Class[1];
partypes[0] = Integer.TYPE;
Method openMethod = oracleClobClass.getDeclaredMethod("open",partypes);
Field modeReadWriteField = oracleClobClass.getField("MODE_READWRITE");
arglist = new Object[1];

arglist[0] = modeReadWriteField.get(null);

openMethod.invoke(tempClob,arglist);
Method getCharacterOutputStreamMethod = oracleClobClass.getDeclaredMethod("getCharacterOutputStream",null);
Writer tempClobWriter = (Writer) getCharacterOutputStreamMethod.invoke(tempClob,null);
tempClobWriter.write((String)value);
tempClobWriter.flush();
tempClobWriter.close();

Method closeMethod = oracleClobClass.getDeclaredMethod("close",null);
closeMethod.invoke(tempClob,null);
st.setClob(index,(Clob)tempClob);

} catch (ClassNotFoundException e) {
throw new HibernateException("Unable to find a required class.\n" + e.getMessage());
} catch (NoSuchMethodException e) {
throw new HibernateException("Unable to find a required method.\n" + e.getMessage());
} catch (NoSuchFieldException e) {
throw new HibernateException("Unable to find a required field.\n" + e.getMessage());
} catch (IllegalAccessException e) {
throw new HibernateException("Unable to find a required method or field.\n" + e.getMessage());
} catch (InvocationTargetException e) {
throw new HibernateException(e.getMessage());
} catch (IOException e) {
throw new HibernateException(e.getMessage());
}
}else {
throw new HibernateException("No CLOBS support. Use drivver version"
+ ORACLE_DRIVER_MAJOR_VERSION
+ ",minor"
+ ORACLE_DRIVER_MINOR_VERSION);
}
} else {
String str = (String) value;
StringReader r = new StringReader(str);
st.setCharacterStream(index,r,str.length());
}
}

@Override
public Object deepCopy(Object value) throws HibernateException {
if(value == null) return null;
return new String((String)value);
}

@Override
public boolean isMutable() {
return false;
}
}