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我从数据库中获取结果时遇到问题。我正在使用 firebird、c3p0、JDBCTemplate、SpringMVC。

public class InvoiceDaoImpl implements InvoiceDao {
...
    public Invoice getInvoice(int id) {
    List<Invoice> invoice = new ArrayList<Invoice>();
    String sql = "SELECT ID,FILENAME, FILEBODY FROM T_FILES WHERE id=" + id;
    JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
    invoice = jdbcTemplate.query(sql, new InvoiceRowMapper());
    return invoice.get(0);
}....}

二手型号：

public class Invoice {  
private int ID;
private Blob FILEBODY;
private String FILENAME;
getters and setters ...
}

RowMapper 和 Extractor 是标准的。

在 JSP 中，我得到一个 FileStream 并作为文件返回以供下载：

@RequestMapping("admin/file/GetFile/{id}")
public void invoiceGetFile(@PathVariable("id") Integer id, HttpServletResponse response) {

    Invoice invoice = invoiceService.getInvoice(id);
    try {
        response.setHeader("Content-Disposition", "inline;filename=\"" + invoice.getFILENAME() + "\"");
        OutputStream out = response.getOutputStream();
        response.setContentType("application/x-ms-excel");
        IOUtils.copy(invoice.getFILEBODY().getBinaryStream(), out);
        out.flush();
        out.close();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

catalina.out：

datasource.DataSourceTransactionManager - Releasing JDBC Connection [com.mchange.v2.c3p0.impl.NewProxyConnection@566b1836] after transaction
http-nio-8443-exec-29 DEBUG datasource.DataSourceUtils - Returning JDBC Connection to DataSource
http-nio-8443-exec-29 DEBUG resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@4d2dbc65 [managed: 2, unused: 1, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@4ca5c225)
org.firebirdsql.jdbc.FBSQLException: GDS Exception. 335544332. 
**invalid transaction handle (expecting explicit transaction start)**
at org.firebirdsql.jdbc.FBBlobInputStream.<init>(FBBlobInputStream.java:38)
at org.firebirdsql.jdbc.FBBlob.getBinaryStream(FBBlob.java:404)

我不明白为什么我在使用 SELECT 时需要使用事务处理，而不是 UPDATE 或 INSERT？

4

1 回答 1

2

Firebird (and JDBC for that matter) does everything in a transaction, because the transaction determines the visibility of data.

In this specific case the select query was executed within a transaction (presumably an auto-commit), but the blob access is done after the transaction has been committed.

This triggers this specific exception because Jaybird knows it requires a transaction to retrieve the blob, but even if Jaybird had a new transaction accessing the blob wouldn't work as the blob handle is only valid inside the transaction that queried for the blob handle.

You will either need to disable auto commit and only commit after retrieving the blob (which would require extensive changes to your DAO by the looks of it), or your row mapper needs to explicitly load the blob (for example into a byte array).

Another option is to ensure this query is executed using a holdable result set (in which case Jaybird will materialize the blob into a byte array within the Blob instance for you), but I am unsure if JdbcTemplate allows you to specify use of holdable result sets.

于 2014-08-21T10:01:38.053 回答