从sqlite数据库读取blob数据->；jpa（hibernate）

嘿

我想从sqlite数据库读取blob数据，但我总是收到此错误消息

08.05.2012 15:06:28 org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 0, SQLState: null
08.05.2012 15:06:28 org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: not implemented by SQLite JDBC driver

我正在使用JSF、Spring、JPA（hibernate）

Sqlite表结构

CREATE TABLE LOGO ('logo_id' INTEGER PRIMARY KEY NOT NULL, 'logo_data' BLOB)

读取一行的代码：

public void loadLogo() {
    try {
        Query query = entityManager.createNativeQuery("SELECT * FROM logo");
        Vector v = (Vector) query.getSingleResult();
        byte[] blobData = (byte[]) v.elementAt(1);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Sqlite方言：

public class SQLiteDialect extends Dialect implements Serializable {

private static final long serialVersionUID = 1L;

public SQLiteDialect() {
    registerColumnType(Types.BIT, "integer");
    registerColumnType(Types.TINYINT, "tinyint");
    registerColumnType(Types.SMALLINT, "smallint");
    registerColumnType(Types.INTEGER, "integer");
    registerColumnType(Types.BIGINT, "bigint");
    registerColumnType(Types.FLOAT, "float");
    registerColumnType(Types.REAL, "real");
    registerColumnType(Types.DOUBLE, "double");
    registerColumnType(Types.NUMERIC, "numeric");
    registerColumnType(Types.DECIMAL, "decimal");
    registerColumnType(Types.CHAR, "char");
    registerColumnType(Types.VARCHAR, "varchar");
    registerColumnType(Types.LONGVARCHAR, "longvarchar");
    registerColumnType(Types.DATE, "date");
    registerColumnType(Types.TIME, "time");
    registerColumnType(Types.TIMESTAMP, "timestamp");
    registerColumnType(Types.BINARY, "blob");
    registerColumnType(Types.VARBINARY, "blob");
    registerColumnType(Types.LONGVARBINARY, "blob");
    registerColumnType(Types.NULL, "null");
    registerColumnType(Types.BLOB, "blob");
    registerColumnType(Types.CLOB, "clob");
    registerColumnType(Types.BOOLEAN, "integer");

    registerFunction("concat", new VarArgsSQLFunction(
            StandardBasicTypes.STRING, "", "||", ""));
    registerFunction("mod", new SQLFunctionTemplate(
            StandardBasicTypes.INTEGER, "?1 % ?2"));
    registerFunction("substr", new StandardSQLFunction("substr",
            StandardBasicTypes.STRING));
    registerFunction("substring", new StandardSQLFunction("substr",
            StandardBasicTypes.STRING));
}

public boolean supportsIdentityColumns() {
    return true;
}

/*
 * public boolean supportsInsertSelectIdentity() { return true; // As
 * specify in NHibernate dialect }
 */

public boolean hasDataTypeInIdentityColumn() {
    return false; // As specify in NHibernate dialect
}

/*
 * public String appendIdentitySelectToInsert(String insertString) { return
 * new StringBuffer(insertString.length()+30). // As specify in NHibernate
 * dialect append(insertString).
 * append("; ").append(getIdentitySelectString()). toString(); }
 */

public String getIdentityColumnString() {
    // return "integer primary key autoincrement";
    return "integer";
}

public String getIdentitySelectString() {
    return "select last_insert_rowid()";
}

public boolean supportsLimit() {
    return true;
}

protected String getLimitString(String query, boolean hasOffset) {
    return new StringBuffer(query.length() + 20).append(query)
            .append(hasOffset ? " limit ? offset ?" : " limit ?")
            .toString();
}

public boolean supportsTemporaryTables() {
    return true;
}

public String getCreateTemporaryTableString() {
    return "create temporary table if not exists";
}

public boolean dropTemporaryTableAfterUse() {
    return false;
}

public boolean supportsCurrentTimestampSelection() {
    return true;
}

public boolean isCurrentTimestampSelectStringCallable() {
    return false;
}

public String getCurrentTimestampSelectString() {
    return "select current_timestamp";
}

public boolean supportsUnionAll() {
    return true;
}

public boolean hasAlterTable() {
    return false; // As specify in NHibernate dialect
}

public boolean dropConstraints() {
    return false;
}

public String getAddColumnString() {
    return "add column";
}

public String getForUpdateString() {
    return "";
}

public boolean supportsOuterJoinForUpdate() {
    return false;
}

public String getDropForeignKeyString() {
    throw new UnsupportedOperationException(
            "No drop foreign key syntax supported by SQLiteDialect");
}

public String getAddForeignKeyConstraintString(String constraintName,
        String[] foreignKey, String referencedTable, String[] primaryKey,
        boolean referencesPrimaryKey) {
    throw new UnsupportedOperationException(
            "No add foreign key syntax supported by SQLiteDialect");
}

public String getAddPrimaryKeyConstraintString(String constraintName) {
    throw new UnsupportedOperationException(
            "No add primary key syntax supported by SQLiteDialect");
}

public boolean supportsIfExistsBeforeTableName() {
    return true;
}

public boolean supportsCascadeDelete() {
    return false;
}

}

请帮帮我

---

感谢

例如，谷歌的智慧表明，尽管SQLite JDBC驱动程序确实支持BLOB支持，但它实际上并没有提供所有的正常操作。例如，它实现

setBytes

，但不实现

setBinaryStream

。通常的解决方法只是调整访问数据的方式

---

由于您没有得到堆栈跟踪，因此不清楚这是否是您的问题；您应该尝试让Hibernate为您提供堆栈跟踪，而不仅仅是异常消息。如果您的问题是由这种部分支持引起的，您必须让Hibernate改变其访问blob的方式（抱歉，不知道如何），或者在Hibernate背后使用

PreparedStatement

。

确定。我有一个解决办法。我必须自己进行sql处理

我有一个从数据库读取数据的静态方法（静态，因为@Inject不能在Servlet中使用）

我实现了一个HttpServlet：

@WebServlet("/images/*")
public class ImageServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    OutputStream os = resp.getOutputStream();
    byte[] temp = LogoServiceImpl.loadLogo();
    os.write(temp);
}

}

在页面上，我只需要指定以下内容，就可以在页面上显示我的图片

<img src="images/xx" />

我还必须将这些行添加到web.xml文件中

<servlet>
    <servlet-name>Image Servlet</servlet-name>
    <servlet-class>at.beko.rainstar2.ui.controller.ImageServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>Image Servlet</servlet-name>
    <url-pattern>/images/*</url-pattern>
</servlet-mapping>

图像Servlet
at.beko.rainstar2.ui.controller.ImageServlet
图像Servlet
/图像/*

我用这种方式存储图像文件

@Override
public void saveLogo(UploadedFile file) {
    try {
        Query query = entityManager
                .createNativeQuery("INSERT INTO 'logo' VALUES (?,?)");
        query.setParameter(1, "2");
        query.setParameter(2, getBytesFromFile(file));
        query.executeUpdate();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

private byte[] getBytesFromFile(UploadedFile file) throws IOException {
    InputStream is = file.getInputstream();

    long length = file.getSize();
    if (length > Integer.MAX_VALUE) {
        // File is too large
    }

    byte[] bytes = new byte[(int) length];

    int offset = 0;
    int numRead = 0;
    int realLength = bytes.length;
    while (offset < realLength
            && (numRead = is.read(bytes, offset, realLength - offset)) >= 0) {
        offset += numRead;
    }

    if (offset < realLength) {
        throw new IOException("Could not completely read file "
                + file.getFileName());
    }

    is.close();
    return bytes;
}

@覆盖
public void saveLogo（上传文件）{
试一试{
Query=entityManager
.createNativeQuery（“插入“徽标”值（？，）”；
query.setParameter（1，“2”）；
setParameter（2，getBytesFromFile（文件））；
query.executeUpdate（）；
}捕获（IOE异常）{
//TODO自动生成的捕捉块
e、 printStackTrace（）；
}
}
私有字节[]getBytesFromFile（UploadedFile文件）引发IOException{
InputStream=file.getInputstream（）；
long length=file.getSize（）；
if（长度>整数最大值）{
//文件太大
}
字节[]字节=新字节[（int）长度]；
整数偏移=0；
int numRead=0；
int realLength=bytes.length；
while（偏移量<实长度
&&（numRead=is.read（字节、偏移量、realLength-offset））>=0）{
偏移量+=numRead；
}
if（偏移量<实长度）{
抛出新IOException（“无法完全读取文件”
+getFileName（））；
}
is.close（）；
返回字节；
}

---

这是我事先的解决办法！！因此，不要介意硬编码部分^^

“不由SQLite JDBC驱动程序实现”非常清楚：除非您自己实现支持，否则无法使用此驱动程序读取blob。但是将blob数据写入数据库不会有问题！这是怎么做到的？？是否有其他SQLite JDBC驱动程序实现或如何实现这种支持的示例？！谢谢你的快速回答。我试图以这种方式使用准备好的声明。首先，我得到带有entity.Manager.unawp（Session.class）的会话；然后我调用doWork函数session.doWork（）{execute（Connection con）{….}，在execute函数中，我使用con.prepareStatement（“SELECT*FROM logo”）创建准备好的语句；接下来我使用ResultSet获取blob字节。但是现在我得到了错误“ResultSet closed”，并且SQLState仍然为null。

@Override
public void saveLogo(UploadedFile file) {
    try {
        Query query = entityManager
                .createNativeQuery("INSERT INTO 'logo' VALUES (?,?)");
        query.setParameter(1, "2");
        query.setParameter(2, getBytesFromFile(file));
        query.executeUpdate();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

private byte[] getBytesFromFile(UploadedFile file) throws IOException {
    InputStream is = file.getInputstream();

    long length = file.getSize();
    if (length > Integer.MAX_VALUE) {
        // File is too large
    }

    byte[] bytes = new byte[(int) length];

    int offset = 0;
    int numRead = 0;
    int realLength = bytes.length;
    while (offset < realLength
            && (numRead = is.read(bytes, offset, realLength - offset)) >= 0) {
        offset += numRead;
    }

    if (offset < realLength) {
        throw new IOException("Could not completely read file "
                + file.getFileName());
    }

    is.close();
    return bytes;
}