hibernate - Apache derby in-memory db schema dump with Hibernate 4+

Question

我在单元测试中使用 Apache Derby 10.9.x 和 Hibernate Entitymanager 4.1.9.Final。 Derby db 模式是从 JPA 注释实体生成的。只有一个 persistence.xml 配置文件。我想在单元测试期间/之前/之后转储生成的 Derby db 模式。这样做的程序化方式是什么？

解决方案:

    // should not be required because Hibernate already started Derby:
    //Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();

    try (Connection conn = DriverManager.getConnection ("jdbc:derby:memory:unit-testing;")) {
        String cat = null;
        String schema = "ROOT";

        DatabaseMetaData md = conn.getMetaData();
        ResultSet rs = md.getTableTypes();
        ResultSetUtils.dump(rs);
        rs = md.getTables(cat, schema, null, new String[]{"TABLE"});
        ResultSetUtils.dump(rs);
        rs = md.getColumns(cat, schema, null, null);
        ResultSetUtils.dump(rs);
    }

公共(public)类 ResultSetUtils {

private static final Logger logger = Logger.getLogger(ResultSetUtils.class.getName());
private static final String COL_SEPARATOR = ";";

public static int getColForLabel(ResultSet rs, String labelname) throws SQLException {
    ResultSetMetaData rsmd = rs.getMetaData();

    for (int i = 1; i <= rsmd.getColumnCount(); i++) {
        if (labelname.equals(rsmd.getColumnLabel(i))) {
            return i;
        }
    }

    throw new SQLException("Invalid label name " + labelname);
}

public static void dump(ResultSet rs) throws SQLException {

    // the order of the rows in a cursor
    // are implementation dependent unless you use the SQL ORDER statement
    ResultSetMetaData meta = rs.getMetaData();
    int colmax = meta.getColumnCount();
    int i;
    Object o;

    StringBuilder sb = new StringBuilder(512);
    for (i = 0; i < colmax; ++i) {
        if(i>0) {
            sb.append(COL_SEPARATOR);
        }
        String s = meta.getColumnName(i + 1);
        sb.append((s == null) ? "NULL" : s);
        s = meta.getColumnTypeName(i + 1);
        sb.append((s == null) ? "(NULL)" : "("+s+")");
    }
    logger.info(sb.toString());


    // the result set is a cursor into the data.  You can only
    // point to one row at a time
    // assume we are pointing to BEFORE the first row
    // rs.next() points to next row and returns true
    // or false if there is no next row, which breaks the loop
    for (; rs.next();) {
        sb = new StringBuilder(512);
        for (i = 0; i < colmax; ++i) {
            if(i>0) {
                sb.append(COL_SEPARATOR);
            }
            o = rs.getObject(i + 1);    // Is SQL the first column is indexed
            sb.append((o == null) ? "NULL" : o.toString());
        }

        logger.info(sb.toString());
    }
}

}

Answer 1

访问模式的编程方式是使用 DatabaseMetaData 类:http://docs.oracle.com/javase/6/docs/api/java/sql/DatabaseMetaData.html

从 getTables() 方法开始，打印出返回的信息。