到postgresql数据库的Java连接
第一次在这里问问题,请原谅我做错了什么 我与java中的postgresql连接如下: Maven xml文件:到postgresql数据库的Java连接,java,postgresql,maven,Java,Postgresql,Maven,第一次在这里问问题,请原谅我做错了什么 我与java中的postgresql连接如下: Maven xml文件: <?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="ht
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>SQL_Database</groupId>
<artifactId>SQL_Database</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.1.1</version>
</dependency>
</dependencies>
</project>
Sql.java:
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
class Sql {
private Connection conn;
private ResultSet results;
public Sql(Connection conn) {
this.conn = conn;
}
public void update(String query) {
try {
this.conn.prepareStatement(query).executeUpdate();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
public void select(String query) {
try {
this.results = this.conn.prepareStatement(query).executeQuery();
getResults();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
和Main.java:
import java.sql.Connection;
public class Main {
public static void main(String args[]){
Connect c = new Connect();
c.setConnection("foo", "foo", "foo");
Connection conn = c.getConnection();
Sql sql = new Sql(conn);
String query = <Some SQL statement>;
sql.update(query);
sql.select(<Some SQL statement>);
c.closeConnection();
}
}
另外,很抱歉出现代码炸弹。这是因为您的代码不在方法中 应该是这样的:-
public class Main extends Application {
public void connect() { // <-- Method declaration
Connect c = new Connect();
c.setConnection("foo", "foo", "foo");
Connection conn = c.getConnection();
Sql sql = new Sql(conn);
//-- Some other code that works perfectly without the above--
}
}
public类主扩展应用程序{
public void connect(){/这是因为您的代码不在方法中
应该是这样的:-
public class Main extends Application {
public void connect() { // <-- Method declaration
Connect c = new Connect();
c.setConnection("foo", "foo", "foo");
Connection conn = c.getConnection();
Sql sql = new Sql(conn);
//-- Some other code that works perfectly without the above--
}
}
public类主扩展应用程序{
public void connect(){//您能给我们看一下项目中不起作用的代码吗?并粘贴错误消息。我将把代码添加到我的帖子中。我尝试运行它时遇到的错误是:错误:(22,20)java:预期错误:(22,21)java:非法启动类型错误:(22,39)java:非法启动类型错误:(22,48)java:类型的非法开始你有是的,这是伪代码,对不起。我已经更正了我的代码。你能给我们看一下项目中不起作用的代码吗?并粘贴错误消息。我将把代码添加到我的帖子中。我试着运行它时遇到的错误是:错误:(22,20)java:预期错误:(22,21)java:非法启动类型错误:(22,39)java:非法启动类型错误:(22,48)java:类型的非法开始你得到了是的,这是伪代码,对不起。我已经更正了我的代码。谢谢!这成功了!谢谢!这成功了!
public class Main extends Application {
public void connect() { // <-- Method declaration
Connect c = new Connect();
c.setConnection("foo", "foo", "foo");
Connection conn = c.getConnection();
Sql sql = new Sql(conn);
//-- Some other code that works perfectly without the above--
}
}