Java &引用；“结果集已关闭”；嵌套执行查询时出错

我想编写一个查询，用java打印数据库中xml标记的值

<employee emp:empid=" " emp:empname="" /><location loc:locname=" "/>

---

使用同一语句打开rs1后，请输入这行代码

  element.setAttributeNS(loc,"loc:locaname",rs.getString(1));}  

将抛出异常，因为它正在处理旧的结果集（rs）

语句类状态的Javadocs：

/**
 * <P>The object used for executing a static SQL statement
 * and returning the results it produces.
 * <P>
 * By default, only one <code>ResultSet</code> object per <code>Statement</code>
 * object can be open at the same time. Therefore, if the reading of one 
 * <code>ResultSet</code> object is interleaved
 * with the reading of another, each must have been generated by
 * different <code>Statement</code> objects. All execution methods in the
 * <code>Statement</code> interface implicitly close a statment's current 
 * <code>ResultSet</code> object if an open one exists.
 *
 * @see Connection#createStatement
 * @see ResultSet 
 */

---

使用同一语句打开rs1后，请输入这行代码

  element.setAttributeNS(loc,"loc:locaname",rs.getString(1));}  

将抛出异常，因为它正在处理旧的结果集（rs）

语句类状态的Javadocs：

/**
 * <P>The object used for executing a static SQL statement
 * and returning the results it produces.
 * <P>
 * By default, only one <code>ResultSet</code> object per <code>Statement</code>
 * object can be open at the same time. Therefore, if the reading of one 
 * <code>ResultSet</code> object is interleaved
 * with the reading of another, each must have been generated by
 * different <code>Statement</code> objects. All execution methods in the
 * <code>Statement</code> interface implicitly close a statment's current 
 * <code>ResultSet</code> object if an open one exists.
 *
 * @see Connection#createStatement
 * @see ResultSet 
 */

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换句话说，我相信蝎子所说的是，你需要一个新的rs1声明。尝试添加如下新语句：

connection = dataSource.getConnection();
ResultSet rs;
connection.setAutoCommit(false);
System.out.println("Connected to server OELDBSQL!!!");
Statement stmt = connection.createStatement();

String querystring = "select empid,empname from empt";

rs = stmt.executeQuery(querystring);
Element child1 = doc.createElement("employee");
try {
    while (rs.next()) {
        child1.setAttributeNS(emp, "emp:empid", rs.getString(1));
        child1.setAttributeNS(emp, "emp:empname", rs.getString(2));
    }
        String querystring1 = "select locname from Locate";
        Statement stmt1 = connection.createStatement();
        ResultSet rs1;
        rs1 = stmt1.executeQuery(querystring1);
        while (rs1.next()) {
            Element element = doc.createElement("location");
            child1.appendChild(element);

            element.setAttributeNS(loc, "loc:locaname", rs.getString(1));
        }
    } catch (Exception e) {
        System.out.println("Exception in connecting to DB"
                + e.getMessage());
        System.err.println(e.getMessage());
    }
} catch (Exception e) {
    System.out
            .println("Exception in connecting to DB" + e.getMessage());
    System.err.println(e.getMessage());
}

---

我还注意到您没有关闭结果集/语句/连接。我强烈建议你关闭它们（按照与创建相反的顺序）。

换句话说，我相信Scorpion所说的是你需要rs1的新声明。尝试添加如下新语句：

connection = dataSource.getConnection();
ResultSet rs;
connection.setAutoCommit(false);
System.out.println("Connected to server OELDBSQL!!!");
Statement stmt = connection.createStatement();

String querystring = "select empid,empname from empt";

rs = stmt.executeQuery(querystring);
Element child1 = doc.createElement("employee");
try {
    while (rs.next()) {
        child1.setAttributeNS(emp, "emp:empid", rs.getString(1));
        child1.setAttributeNS(emp, "emp:empname", rs.getString(2));
    }
        String querystring1 = "select locname from Locate";
        Statement stmt1 = connection.createStatement();
        ResultSet rs1;
        rs1 = stmt1.executeQuery(querystring1);
        while (rs1.next()) {
            Element element = doc.createElement("location");
            child1.appendChild(element);

            element.setAttributeNS(loc, "loc:locaname", rs.getString(1));
        }
    } catch (Exception e) {
        System.out.println("Exception in connecting to DB"
                + e.getMessage());
        System.err.println(e.getMessage());
    }
} catch (Exception e) {
    System.out
            .println("Exception in connecting to DB" + e.getMessage());
    System.err.println(e.getMessage());
}

---

我还注意到您没有关闭结果集/语句/连接。我强烈建议您关闭它们（以与创建相反的顺序）。

我尝试了使用while循环和single resultset.querystring，但没有使用try块=“从emptlocate中选择emp.empid、emp.empname、locate.locname；然后它给出多个值意味着假设空表有5个名称。这五个名称与locname重复5次。iam获得25行，而不是5行。我尝试使用while loop with single resultset.querystring=“从Empts、locate中选择Empts.empid、Empts.empname、locate.locname；然后它给出多个值意味着假设Empts表有5个名称。这五个名称与locname重复5次。iam获得25行，而不是5行