使用 hibernate 将 blob 保存到数据库

Question

我尝试使用 blob 和 hibernate3 将文件保存到 MySQL。但我一直都有 java.lang.UnsupportedOperationException：无法通过创建会话来操作 Blob org.hibernate.lob.BlobImpl.excep(BlobImpl.java:127)

这里有一些代码。

package com.uni.domain;

public class File extends Identifier {

    private byte[] data;
    private String contentType;

    public byte[] getData() {
        return data;
    }

    public File() {}

    public void setData(byte[] photo) {
        this.data = photo;
    }

    public boolean isNew() {
        return true;
    }

    public String getContentType() {
        return contentType;
    }

    public void setContentType(String contentType) {
        this.contentType = contentType;
    }
}

package com.uni.domain;

import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.usertype.UserType;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.sql.*;
import java.util.Arrays;

public class PhotoType implements UserType {

    public int[] sqlTypes() {
        return new int[]{Types.BLOB};
    }

    public Class returnedClass() {
        return byte[].class;
    }

    public boolean equals(Object o, Object o1) throws HibernateException {
        return Arrays.equals((byte[]) o, (byte[]) o1);
    }

    public int hashCode(Object o) throws HibernateException {
        return o.hashCode();
    }

    public Object nullSafeGet(ResultSet resultSet, String[] strings, Object o) throws HibernateException, SQLException {
        Blob blob = resultSet.getBlob(strings[0]);
        return blob.getBytes(1, (int) blob.length());
    }

    public void nullSafeSet(PreparedStatement st, Object value, int index)
            throws HibernateException, SQLException {
        st.setBlob(index, Hibernate.createBlob((byte[]) value));
    }

    public Object deepCopy(Object value) {
        if (value == null) return null;

        byte[] bytes = (byte[]) value;
        byte[] result = new byte[bytes.length];
        System.arraycopy(bytes, 0, result, 0, bytes.length);

        return result;
    }

    public boolean isMutable() {
        return true;
    }

    public Serializable disassemble(Object o) throws HibernateException {
        return null;  .
    }

    public Object assemble(Serializable serializable, Object o) throws HibernateException {
        return null;  .
    }

    public Object replace(Object o, Object o1, Object o2) throws HibernateException {
        return null;  .
    }

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.uni.domain">
    <class name="com.uni.domain.File">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="data" type="com.uni.domain.FleType"/>
        <property name="contentType"/>
    </class>
</hibernate-mapping>

请帮助我。我哪里错了？

Answer 1

如果你查看BlobImpl的hibernate源代码，你会发现getBytes方法没有实现，并且只转发到异常：

  69    /**
   70        * @see java.sql.Blob#getBytes(long, int)
   71        */
   72       public byte[] getBytes(long pos, int len) throws SQLException {
   73           excep(); return null;
   74       }

 126    private static void excep() {
  127           throw new UnsupportedOperationException("Blob may not be manipulated from creating session");
  128       }
  129   

而不是 getBytes() 你应该使用 getBinaryStream()

示例用法：

    InputStream inputStream = getContent().getBinaryStream();
    int expected = inputStream.available();
    byte[] contents = new byte[expected];
    int length = inputStream.read(contents);
    if(length != expected)
            throw new IOException("Could not read full input");

Answer 2

如果您将其与 Spring 一起使用，则 Spring 对其有内置支持。 DefaultLobHandler< /a> 这是让它工作的配置问题。 示例代码供参考，与旧版本相比没有太大变化春天。