我在 servlet 上下文启动时通过以下代码在 H2 数据库中创建内存数据库
void initDb() {
try {
webserver = Server.createWebServer().start();
Class.forName("org.h2.Driver");
Connection conn = DriverManager.getConnection("jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1","SA","");
InputStream in = getClass().getResourceAsStream("script.sql");
if (in == null) {
System.out.println("Please add the file script.sql to the classpath, package " + getClass().getPackage().getName());
} else {
RunScript.execute(conn, new InputStreamReader(in));
Statement stat = conn.createStatement();
ResultSet rs = stat.executeQuery("SELECT TO_CHAR(bday,'DD/MM/yyyy hh24:mi') FROM TEST2");
while (rs.next()) {
System.out.println(rs.getString(1));
}
rs.close();
stat.close();
conn.commit();
conn.close();
}
//accessed using url jdbc:h2:tcp://localhost/mem:db1
try{
CachedRowSet crs = new DBConnector().executeQuery("select * from test2");
while(crs.next()){
System.out.println("ARGUMENT_NAME:"+crs.getString(1));
// System.out.println(",DATA_TYPE:"+crs.getString("DATA_TYPE"));
}
crs.close();
}catch(SQLException e){
e.printStackTrace();
}
} catch (Exception e) { //this exception gets throws connection failed!
System.out.println("Exception initializing memory H2 database"+e);
}
}
我稍后通过 url 访问
jdbc:h2:mem:db1
在同一个 JVM 中,它也在工作。但是当我想通过 jdbc:h2:tcp://localhost/mem:db1
访问它时它在同一个 JVM 或不同的 JVM 中都不起作用。我实际上想以嵌入式模式运行系统并使用控制台查看内容。如果我以相同的 servlet 上下文启动方法启动网络服务器,我可以看到控制台,但它仍然没有连接到带有 url
jdbc:h2:tcp://localhost/mem:db1
的内存数据库。 .如果我使用命令行启动服务器
java -cp "WebContent/WEB-INF/lib/h2-1.3.148.jar;hsqldb.jar;%H2DRIVERS%;%CLASSPATH%" org.h2.tools.Console %*
and url as 'jdbc:h2:tcp://localhost/mem:db1'
然后尝试连接,令人惊讶的是它连接但没有数据。似乎它正在自己创建一个单独的服务器和一个不同的数据库。所以没有数据。
最佳答案
要使内存数据库可用于另一个进程,您需要在打开数据库的同一进程中启动 TCP 服务器。例子:
package db;
import java.sql.Connection;
import java.sql.DriverManager;
import org.h2.tools.Server;
public class TestMem {
public static void main(String... args) throws Exception {
// open the in-memory database within a VM
Class.forName("org.h2.Driver");
Connection conn = DriverManager.getConnection("jdbc:h2:mem:test");
conn.createStatement().execute("create table test(id int)");
// start a TCP server
// (either before or after opening the database)
Server server = Server.createTcpServer().start();
// .. use in embedded mode ..
// or use it from another process:
System.out.println("Server started and connection is open.");
System.out.println("URL: jdbc:h2:" + server.getURL() + "/mem:test");
// now start the H2 Console here or in another process using
// java org.h2.tools.Console -web -browser
System.out.println("Press [Enter] to stop.");
System.in.read();
System.out.println("Stopping server and closing the connection");
server.stop();
conn.close();
}
}
关于embedded-database - Console无法访问内存模式下的H2数据库,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5077584/