JDBC Statement RETURN_GENERATED_KEYS返回自动生成的ID

梦里梦外; 2023-09-26 10:12 83阅读 0赞

Java 语句 RETURN\_GENERATED\_KEYS 指示生成的密钥应可用于检索的常量。

#### 语法 ####

语句中的字段RETURN\_GENERATED\_**KEYS**（） 声明为：

复制

int RETURN_GENERATED_KEYS = 1;

#### 例 ####

下面的代码演示如何使用 Java Statement.RETURN\_GENERATED\_KEYS

示例 1

import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.Statement;
    
    public class Main {
        private static final String URL = "jdbc:mysql://localhost/testdb";
    
        private static final String USERNAME = "root";
    
        private static final String PASSWORD = "";
    
        public static void main(String[] args) throws Exception {
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
    
            String insert = "INSERT INTO orders (username, order_date) VALUES ('foobar', '2007-12-13')";
            Statement stmt = conn.createStatement();
    
            stmt.executeUpdate(insert, Statement.RETURN_GENERATED_KEYS);
    
            ResultSet keys = stmt.getGeneratedKeys();
            int lastKey = 1;
            while (keys.next()) {
                lastKey = keys.getInt(1);//    ww  w  .    d e   m  o2    s . c   o   m
            }
            System.out.println("Last Key: " + lastKey);
            conn.close();
        }
    }

另一种方法：

import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.Statement;
    
    public class Main {
    
        private static final String URL = "jdbc:mysql://localhost/testdb";
    
        private static final String USERNAME = "root";
    
        private static final String PASSWORD = "root";
    
        public static void main(String[] args) throws Exception {
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
    
            String insert = "INSERT INTO orders (username, order_date) VALUES ('foobar', '2007-12-13')";
            Statement stmt = conn.createStatement();
    
            String[] id_col = {"id"};
            stmt.executeUpdate(insert, id_col);
    
            ResultSet keys = stmt.getGeneratedKeys();
            int lastKey = 1;
            while (keys.next()) {
                lastKey = keys.getInt(1);
            }
            System.out.println("Last Key: " + lastKey);
            conn.close();
        }
    }

示例 2

复制

import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class Main {
        public static void main(String[] args) throws Exception {
            String url = "jdbc:mysql://localhost/testdb";
            String username = "root";
            String password = "";
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = null;/*w   w  w   .d   e  m o  2   s .    c o   m*/
            try {
                conn = DriverManager.getConnection(url, username, password);
                conn.setAutoCommit(false);
    
                Statement st = conn.createStatement();
                st.execute("INSERT INTO orders (username, order_date) VALUES ('java', '2007-12-13')",
                        Statement.RETURN_GENERATED_KEYS);
    
                ResultSet keys = st.getGeneratedKeys();
                int id = 1;
                while (keys.next()) {
                    id = keys.getInt(1);
                }
                PreparedStatement pst = conn.prepareStatement(
                        "INSERT INTO order_details (order_id, product_id, quantity, price) VALUES (?, ?, ?, ?)");
                pst.setInt(1, id);
                pst.setString(2, "1");
                pst.setInt(3, 10);
                pst.setDouble(4, 100);
                pst.execute();
    
                conn.commit();
                System.out.println("Transaction commit...");
            } catch (SQLException e) {
                if (conn != null) {
                    conn.rollback();
                    System.out.println("Connection rollback...");
                }
                e.printStackTrace();
            } finally {
                if (conn != null && !conn.isClosed()) {
                    conn.close();
                }
            }
        }
    }

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[Link 1]: https://www.demo2s.com/java/java-statement-getgeneratedkeys.html
[Link 2]: https://www.demo2s.com/java/java-statement-getmaxrows.html
[Java _ executeUpdate_String sql_ int columnIndexes]: https://www.demo2s.com/java/java-statement-executeupdate-string-sql-int-columnindexes.html
[Java _String sql_ String _]: https://www.demo2s.com/java/java-statement-executeupdate-string-sql-string-columnnames.html
[Java]: https://www.demo2s.com/java/java-statement-getmaxfieldsize.html
[Java _ getQueryTimeout]: https://www.demo2s.com/java/java-statement-getquerytimeout.html