Question

HY！

我想从sqlite数据库中读取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（休眠）。

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;
}

}

请帮助我！

由于

Answer 1

Google的智慧，例如here，建议虽然SQLite JDBC驱动程序支持BLOB支持，但它实际上并不提供所有正常操作。例如，它实现setBytes但不实现setBinaryStream。通常的解决方法是调整您访问数据的方式。

由于您没有获得堆栈跟踪，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Exception消息。如果您的问题是由这种部分支持引起的，那么您必须让Hibernate改变其访问Blob的方式（不知道如何，对不起），或者使用PreparedStatement代替Hibernate。

Answer 2

确定。我有一个解决方案。我必须自己进行sql处理。

我有一个静态方法从数据库中读取数据（静态，因为@Inject不能在Servlet中使用）

public static byte[] loadLogo() {
    byte[] ar = null;
    Connection con;
    Statement stmt;
    String driver = "org.sqlite.JDBC";
    String url = "jdbc:sqlite:X:\\Projekte\\Bauer - Rainstar\\Entwickler\\database\\rainstar_ds.sqlite";
    try {
        Class.forName(driver).newInstance();
        con = DriverManager.getConnection(url);
        con.setAutoCommit(false);

        stmt = con.createStatement();

        ResultSet set = stmt.executeQuery("SELECT * FROM logo");
        set.next();
        ar = set.getBytes("logo_data");

        con.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

    return ar;
}

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);
}

}

在页面上我只需指定以下内容，即可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

<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>

我以这种方式存储了我的图像文件。

@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;
}

这是我的预先解决方案!!所以不要介意硬编码的部分^^

从sqlite数据库中读取blob数据 - ＆gt; jpa（休眠）

2 个答案: