Hibernate createNativeQuery returning Proxy object

问题:

I am forced into a situation where i am using hibernate createNativeQuery to return a List of Objects arrays.

One of the (many) columns from which my query returns values is a CLOB.

The Object which is returned is com.sun.Proxy object.

I have seen a question here where

getClass().getInterfaces()

was used to identify that it is a WrappedClob being returned.

However given that I now have this proxy object in my Java code, how do I convert it into something useful ... like a String?

回答1:

The following code helped to unProxy the clob

Link which help me, just add a bit of makeup to the code :D

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Clob;
import java.sql.SQLException;
    /**
         * Unproxy clob.
         *
         * @param proxy the proxy
         * @return the string
         * @throws InvocationTargetException the invocation target exception
         * @throws IntrospectionException the introspection exception
         * @throws IllegalAccessException the illegal access exception
         * @throws SQLException the SQL exception
         * @throws IOException Signals that an I/O exception has occurred.
         */
        public static String unproxyClob(Object proxy)
            throws InvocationTargetException, IntrospectionException, IllegalAccessException, SQLException, IOException {
            try {
                BeanInfo beanInfo = Introspector.getBeanInfo(proxy.getClass());
                for (PropertyDescriptor property : beanInfo.getPropertyDescriptors()) {
                    Method readMethod = property.getReadMethod();
                    if (readMethod.getName().contains(GET_WRAPPED_CLOB)) {
                        Object result = readMethod.invoke(proxy);
                        return clobToString((Clob) result);
                    }
                }
            } catch (InvocationTargetException | IntrospectionException | IllegalAccessException | SQLException | IOException exception) {
                LOGGER.fatal(exception);
                throw exception;
            }
            return null;
        }

        /**
         * Clob to string.
         *
         * @param data the data
         * @return the string
         * @throws SQLException the SQL exception
         * @throws IOException Signals that an I/O exception has occurred.
         */
        public static String clobToString(Clob data) throws SQLException, IOException {
            StringBuilder sb = new StringBuilder();
            Reader reader = data.getCharacterStream();
            BufferedReader br = new BufferedReader(reader);
            String line;
            while (null != (line = br.readLine())) {
                sb.append(line);
            }
            br.close();

            return sb.toString();
        }

回答2:

You can try this code. Probably it is not perfect, but it works for me :) I'm using it to convert regular clob to string so it should also work if you unwrap clob object with getWrappedClob()

Clob clob = wrappedClob.getWrappedClob();
String result = null;
Long length = clob.length();
char[] char_array = new char[length.intValue()];
Reader characterStream = clob.getCharacterStream();
try {
    int read = characterStream.read(char_array, 0, length.intValue());
    result = new String(char_array);
} catch (IOException e) {
    log.error("Exception during read from CLOB: " + e);
}