eclipse 如何从 Java 和 H2 DB 连接到 H2 数据库
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How to connect to H2 database from Java & H2 DB
提问by seulberg1
I am fairly new to Eclipse & Java and currently work on a project where I need to implement my first database.
我对 Eclipse 和 Java 还很陌生，目前正在从事一个需要实现我的第一个数据库的项目。
Therefore, I tried to connect Eclipse and the H2 Database. While the H2 database part works just fine by itself, I can't figure out how to connect it to Eclipse.
因此，我尝试连接 Eclipse 和 H2 数据库。虽然 H2 数据库部分本身工作得很好，但我不知道如何将它连接到 Eclipse。
I created the following class and tried to do everything as stated on the website:
我创建了以下课程并尝试按照网站上的说明执行所有操作：
package srpTracking;
import java.sql.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import org.h2.tools.DeleteDbFiles;
public class DatabaseConnector {
public static void main(String... args) throws Exception {
DeleteDbFiles.execute("~", "test", true);
Class.forName("org.h2.Driver");
Connection conn = DriverManager.getConnection("jdbc:h2:~/test");
Statement stat = conn.createStatement();
stat.execute("create table test(id int primary key, name varchar(255))");
stat.execute("insert into test values(1, 'Hello')");
ResultSet rs;
rs = stat.executeQuery("select * from test");
while (rs.next()) {
System.out.println(rs.getString("name"));
}
}
stat.close();
conn.close();
}
I get identifier errors for the last two lines of code, but it also doesn't connect anything.
我收到最后两行代码的标识符错误，但它也没有连接任何东西。
I copied the H2.jar file into the project folder in a subfolder called lib.
我将 H2.jar 文件复制到名为 lib 的子文件夹中的项目文件夹中。
Unfortunately I can't for some reason install the DTP plugin, because I am apparently missing a 'org.eclipse.core.runtime' file.
不幸的是，由于某种原因我无法安装 DTP 插件，因为我显然缺少一个“org.eclipse.core.runtime”文件。
What do I need to change about my code connect Java and H2? Also, do I need to copy and H2 files into specific folders?
我需要对连接 Java 和 H2 的代码进行哪些更改？另外，我是否需要将 H2 文件复制到特定文件夹中？
采纳答案by Jan
Consider these changes to your main. By using try-with-resource you delegate the close to the JVM - with the added benefit that even in cases of exceptions, you wouldn't need to close them as well.
考虑对您的 main.js 进行这些更改。通过使用 try-with-resource，您可以将关闭委托给 JVM - 具有额外的好处，即使在出现异常的情况下，您也不需要关闭它们。
Why it didn't work before? Your variables ran out of scope- you tried to close aftermain() had ended.
为什么以前不起作用？您的变量超出范围- 您试图在main() 结束后关闭。
public static void main(String... args) throws Exception {
DeleteDbFiles.execute("~", "test", true);
Class.forName("org.h2.Driver");
try (Connection conn = DriverManager.getConnection("jdbc:h2:~/test");
Statement stat = conn.createStatement()) {
stat.execute("create table test(id int primary key, name varchar(255))");
stat.execute("insert into test values(1, 'Hello')");
try (ResultSet rs = stat.executeQuery("select * from test")) {
while (rs.next()) {
System.out.println(rs.getString("name"));
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
