Java h2（嵌入式模式）数据库文件问题
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h2 (embedded mode ) database files problem
提问by aeter
There is a h2-database file in my src directory (Java, Eclipse): h2test.db
我的 src 目录（Java、Eclipse）中有一个 h2-database 文件：h2test.db
The problem:
问题：
starting the h2.jar from the command line (and thus the h2 browser interface on port 8082), I have created 2 tables, 'test1' and 'test2' in h2test.db and I have put some data in them;
when trying to access them from java code (JDBC), it throws me "table not found exception". A "show tables" from the java code shows a resultset with 0 rows.
Also, when creating a new table ('newtest') from the java code (CREATE TABLE ... etc), I cannot see it when starting the h2.jar browser interface afterwards; just the other two tables ('test1' and 'test2') are shown (but then the newly created table 'newtest' is accessible from the java code).
从命令行启动 h2.jar（以及端口 8082 上的 h2 浏览器界面），我在 h2test.db 中创建了 2 个表，“test1”和“test2”，并在其中放入了一些数据；
当尝试从 Java 代码 (JDBC) 访问它们时，它会抛出“找不到表异常”。java 代码中的“显示表”显示了一个具有 0 行的结果集。
另外，当从java代码（CREATE TABLE ...等）创建一个新表（'newtest'）时，我在之后启动h2.jar浏览器界面时看不到它；只显示了另外两个表（'test1' 和 'test2'）（但是新创建的表 'newtest' 可以从 java 代码访问）。
I'm inexperienced with embedded databases; I believe I'm doing something fundamentally wrong here. My assumption is, that I'm accessing the same file - once from the java app, and once from the h2 console-browser interface. I cannot seem to understand it, what am I doing wrong here?
我对嵌入式数据库缺乏经验；我相信我在这里做了一些根本错误的事情。我的假设是，我正在访问同一个文件 - 一次来自 java 应用程序，一次来自 h2 控制台浏览器界面。我似乎无法理解它，我在这里做错了什么？
EDIT: as requested, adding some code:
编辑：根据要求，添加一些代码：
Java code:
爪哇代码：
Class.forName("org.h2.Driver");
String url = "jdbc:h2:" + "db/h2test.db";
String user = "aeter";
String password = "aeter";
Connection conn = DriverManager.getConnection(url, user, password);
PreparedStatement ps2 = conn.prepareStatement("Show tables;");
ResultSet rs = ps2.executeQuery();This resultset has 0 rows (no tables), instead of showing me the 2 tables.
这个结果集有 0 行（没有表格），而不是向我展示 2 个表格。
H2 Console-browser interface settings:
H2 Console-浏览器界面设置：
Settings: Generic h2(embedded) driver class: org.h2.Driver JDBC URL: jdbc:h2:../../workspace/project_name/src/db/h2test.db user name: aeter password: aeter
EDIT2: I copied the database to a new folder. Now the db file in the new folder is shown with the 'newtest' table (from the java code) and with the 'test1' and 'test2' tables (from the console-browser h2 interface) - exactly the same way the older db file was shown. So the problem persists with the copy of the db file.
EDIT2：我将数据库复制到一个新文件夹。现在，新文件夹中的 db 文件与 'newtest' 表（来自 java 代码）以及 'test1' 和 'test2' 表（来自控制台浏览器 h2 界面）一起显示 - 与旧数据库完全相同文件显示。因此问题仍然存在于 db 文件的副本中。
回答by trashgod
For embedded mode, you'll need to check the path. For example, use a path relative to your home directory:
对于嵌入模式，您需要检查路径。例如，使用相对于您的主目录的路径：
"jdbc:h2:file:~/db/h2test.db"
To be sure, use a full path:
可以肯定的是，使用完整路径：
"jdbc:h2:file:/users/aeter/db/h2test.db"
For convenience, append ;IFEXISTS=TRUEto avoid creating spurious database files.
为方便起见，追加;IFEXISTS=TRUE以避免创建虚假的数据库文件。
See Connecting to a Database using JDBCfor more.
有关更多信息，请参阅使用 JDBC 连接到数据库。
H2 ServerURLs are relative to the -baseDirspecified as a parameter to main().
H2服务器URL 相对于-baseDir指定为 的参数main()。
回答by shms
Also you can like this
你也可以喜欢这个
"jdbc:h2:file:db/h2test.db"
then java looks db folder from project folder
然后java从项目文件夹中查找db文件夹
->projectName // project folder
-->src // src folder
-->db // here your database folder
-->....
回答by Aconic
If you are using Hibernate try this in hibernate.cfg.xml file:
如果您正在使用 Hibernate，请在 hibernate.cfg.xml 文件中尝试此操作：
<property name="connection.url">jdbc:h2:file:db/h2test</property>
without *.db extension at the end
最后没有 *.db 扩展名
回答by voho
Also there can be a problem if you use some special parameters in your JDBC url, the database file name can differ for various cases.
如果您在 JDBC url 中使用一些特殊参数，也会出现问题，数据库文件名可能因各种情况而异。
In my case, I had two URLs:
就我而言，我有两个 URL：
- jdbc:h2:~/XXX;MVCC=FALSE;MV_STORE=FALSE
- jdbc:h2:~/XXX
- jdbc:h2:~/XXX;MVCC=FALSE;MV_STORE=FALSE
- jdbc:h2:~/XXX
This first case created XXX.h2.db file, the second one XXX.mv.db, beware.
第一个案例创建了 XXX.h2.db 文件，第二个是 XXX.mv.db，小心。
