JDBC：Connection.close()

https://www.2cto.com/database/201501/369246.html

Connection对象在执行close() 方法之后，并不是直接把Connection对象设置为null （Connection对象有一个方法， isClosed() 判断Connection是否被关闭，如果直接设置为null，再执行isClosed() 就会报空指针异常）

close()源码：

public void close() throws SQLException {

    synchronized (getConnectionMutex()) {

        if (this.connectionLifecycleInterceptors != null) {

            new IterateBlock<Extension>(this.connectionLifecycleInterceptors.iterator()) {

                @Override

                void forEach(Extension each) throws SQLException {

                    ((ConnectionLifecycleInterceptor) each).close();

                }

            }.doForAll();

        }

        realClose(true, true, false, null);

    }

}

测试代码：

DBUtil是自己写的一个工具类，有静态方法 ResultSet generalQuery()，静态属性conn, pst

public class Test {

    public static void main(String[] args) {

        String sql = "select * from member where mId = ? and mPwd = ?";

        Object[] params = {"2015", "1233"};

        ResultSet rs = DBUtil.generalQuery(sql, params);int cnt = 0;

        try {

            if(rs != null) {

                rs.last();

                cnt = rs.getRow();

            }

            if(rs != null) rs.close();

            if(DBUtil.pst != null) DBUtil.pst.close();

            if(DBUtil.conn != null) DBUtil.conn.close();

            if(cnt != 0) {

                System.out.println("查询成功！");

            }else {

                System.out.println("查询失败");

            }

        }catch (SQLException e) {

            e.printStackTrace();

        }

        try {

            System.out.println(DBUtil.conn);  // com.mysql.jdbc.JDBC4Connection@619a5dff

            System.out.println(DBUtil.pst);   // java.sql.SQLException: No operations allowed after statement closed.

            System.out.println(rs); //com.mysql.jdbc.JDBC42ResultSet@23ab930d

            System.out.println(DBUtil.conn.isClosed());  //true

            System.out.println(DBUtil.pst.isClosed());  //true

            System.out.println(rs.isClosed()); //true

        } catch (SQLException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

}

巴特西

JDBC：Connection.close()

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