使用JavaFX+JDK20开发时遇java.sql模块'requires transitive'缺失警告

问题背景 #

用JavaFX结合JDK20、Eclipse开发项目时，数据库操作环节出现警告：java.sql模块的Connection、ResultSet、PreparedStatement等类型因缺少requires transitive声明，可能无法被客户端访问。

警告详情 #

Description Resource    Path    Location    Type
The type Connection from module java.sql may not be accessible to clients due to missing  'requires transitive' dbConnect.java  /myProject/src/mypackage line 25    Java Problem

相关代码 #

dbConnect.java #

package mypackage;
import java.io.IOException;
import java.sql.*;     // 引用java.sql包下的类
import java.util.Properties;

public class dbConnect {
 // 初始化数据库常量
 static final String databaseDriver = "oracle.jdbc.driver.OracleDriver";
 static final String databaseURL = "jdbc:oracle:thin:@localhost:1521:xe";
 static final String username = "system";
 static final String pass = "oracle";
 private Connection connection;
 private Properties properties;
 private Statement statement;

/**
 * 连接数据库  
 * 
 * @return Connection
 */
public Connection connect()
{
    if (connection == null)
    {         
        try {
            Class.forName(databaseDriver);
            connection = (Connection) DriverManager.getConnection
                    (databaseURL, getProperties());
        }
        catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }
    return connection;
}   
// 省略其他代码

module-info.java #

module myProject{
   requires transitive javafx.graphics;
   requires javafx.controls;
   requires javafx.fxml;
   requires javafx.base;
   requires javafx.web;
   requires java.sql;

   opens mypackage to javafx.fxml;
   exports mypackage;
}

解决方案 #

修改module-info.java中的requires java.sql;为requires transitive java.sql;，修改后的模块声明如下：

module myProject{
   requires transitive javafx.graphics;
   requires javafx.controls;
   requires javafx.fxml;
   requires javafx.base;
   requires javafx.web;
   requires transitive java.sql;

   opens mypackage to javafx.fxml;
   exports mypackage;
}

原因说明 #

你的模块通过exports mypackage;对外暴露了mypackage包，而dbConnect类的connect()方法返回了java.sql.Connection类型——这属于java.sql模块的公开类型。当其他模块依赖你的myProject模块并调用该方法时，如果仅用requires java.sql;，客户端模块需要自己显式声明requires java.sql;才能访问这些类型；而requires transitive java.sql;会将java.sql模块的依赖传递给所有依赖myProject的模块，确保客户端能正常访问Connection等类型，同时消除警告。

内容的提问来源于stack exchange，提问作者F.M