check the manual that corresponds to your MySQL server version for the right syntax to use near '?,?

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测试类如下：在执行的过程中一致报上面的错误：

package com.test;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 JDBCUtils1 {    public static void main(String[] args) throws Exception {        System.out.println(getGeneratedKey("dada", "123"));    }    public static Connection conn;    public static String user = "root";    public static  String password = "123456";    public static  String url = "jdbc:mysql://localhost/shiro";    /**     * 获取自增的 ID     * @return     * @throws Exception      */    public static int getGeneratedKey(String username, String password) throws Exception {        Connection conn = getMysqlConn();        String sql = "insert into test (username,password) values (?,?)";        PreparedStatement pstat = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);        pstat.setString(1, username);        pstat.setString(2, password);        pstat.executeUpdate(sql);        ResultSet rs = pstat.getGeneratedKeys();        rs.next();        int key = rs.getInt(1);        return key;    }    /**     * @return 获取 Mysql 连接     * @throws Exception     */    public static Connection getMysqlConn() throws Exception {        if(conn == null) {            Class.forName("org.gjt.mm.mysql.Driver");            conn = DriverManager.getConnection(url, user, password);        }        return conn;    }}

修改后如下：

package com.github.zhangkaitao.shiro.chapter2.realm;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 JDBCUtils1 {    public static void main(String[] args) throws Exception {        System.out.println(getGeneratedKey("dada", "123"));    }    public static Connection conn;    public static String user = "root";    public static  String password = "123456";    public static  String url = "jdbc:mysql://localhost/shiro";    /**     * 获取自增的 ID     * @return     * @throws Exception      */    public static int getGeneratedKey(String username, String password) throws Exception {        Connection conn = getMysqlConn();        String sql = "insert into test (username,password) values (?,?)";        PreparedStatement pstat = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);        pstat.setString(1, username);        pstat.setString(2, password);        pstat.executeUpdate();        ResultSet rs = pstat.getGeneratedKeys();        rs.next();        int key = rs.getInt(1);        return key;    }    /**     * @return 获取 Mysql 连接     * @throws Exception     */    public static Connection getMysqlConn() throws Exception {        if(conn == null) {            Class.forName("org.gjt.mm.mysql.Driver");            conn = DriverManager.getConnection(url, user, password);        }        return conn;    }}

区别：

第一个里面在执行 pstat.executeUpdate(sql); 时候把原始的sql又放进去了，这肯定是有问题的，前面已经设置过值了，现在又设置了一遍 sql 那么前面的东西都被替换掉了，pstmt 执行的内容变成了：“insert into test (username,password) values (?,?)”，这样自然会报错了。其实只需要执行 pstat.executeUpdate()里面什么内容都不需要放，因为前面已经设置过了，再次设置是错误的。

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