Question

我被迫进入一种情况，我正在使用hibernate createNativeQuery来返回一个对象列表数组。

我的查询返回值的（很多）列之一是CLOB。

返回的对象是com.sun.Proxy对象。

我看到了一个问题here 其中

getClass().getInterfaces()

用于识别它是返回的WrappedClob。

但是考虑到我现在在我的Java代码中有这个代理对象，我该如何将它转换为有用的东西...比如String？

Answer 1

以下代码有助于取消隐藏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();
        }

Answer 2

您可以尝试使用此代码。可能它并不完美，但它对我有用:) 我正在使用它将常规clob转换为字符串，所以如果你用getWrappedClob（）

打开clob对象它也应该工作

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);
}

Answer 3

这不是对 OP 问题的直接回答，因为我不必处理“WrappedClob”的实例。但由于我仍然收到相同的误导性错误消息，我希望有人觉得这很有用：

对我来说，问题是，H2 和 Postgres 的“Clob to String”的休眠实现方式不同。因此，虽然我的测试工作正常，但应用程序会在运行时崩溃。为了解决这个问题，我在不同的环境中实例化了 ClobReader 的不同 bean。生产环境将使用 Postgres 的 bean 实现，而测试代码使用 H2 bean。

public interface ClobReader {
    String clobToString(Object clob) throws SQLException, IOException;
}


@Bean
public ClobReader clobReaderPostgres() {
    return new ClobReader() {
        @Override
        public String clobToString(final Object clob) {
            if (clob == null) {
                return null;
            }
            return clob.toString();
        }
    };
}


@Bean
@Primary
public ClobReader clobReaderH2() {
    return new ClobReader() {
        @Override
        public String clobToString(final Object obj) throws SQLException, IOException {
            final Clob clob = (Clob) obj;
            try (final Reader reader = clob.getCharacterStream()) {
                try (final StringWriter stringWriter = new StringWriter()) {
                    IOUtils.copy(reader, stringWriter);
                    return stringWriter.toString();
                }
            }
        }
    };
}

Hibernate createNativeQuery返回Clob的Proxy对象

3 个答案: