如何使 Java ResultSet 在我的 jsp 中可用? [英] How do I make a Java ResultSet available in my jsp?

问题描述

我想为一些构建具有多个参数的复杂查询的 Java 代码替换 sql:query.当前的sql是一个简单的select.

<前><sql:查询变量=结果"数据源="${dSource}"sql="select * from TABLE "></sql:查询>

如何获取我的 Java ResultSet(即 rs = stmt.executeQuery(sql);)并使结果在我的 JSP 中可用，以便我可以编写这本教科书 JSP?

为了更清楚，我想删除上面的查询并用Java替换它.

<前><%结果集 rs = stmt.executeQuery(sql);//杂乱的代码会出现在一些控制器中%>

<前><c:forEach var="row" items="${result.rows}"><c:out value="${row.name}"/></c:forEach>

我是否在 Java 部分设置了 session/page 变量，或者是否有一些 EL 技巧可以用来访问该变量?

解决方案

模型(行):

公共类行{私人字符串名称；//添加/生成构造函数、getter 和 setter.}

DAO:

public Listlist() 抛出 SQLException {连接连接=空；语句语句 = null;结果集 resultSet = null;列表<行>行 = 新的 ArrayList();尝试 {connection = database.getConnection();语句 = connection.createStatement();resultSet = statement.executeQuery(SQL_LIST);而(resultSet.next()){行行 = new Row();row.setName(resultSet.getString("name"));//...行.添加(行)；}} 最后 {if (resultSet != null) try { resultSet.close();} catch (SQLException logOrIgnore) {}if (statement != null) try { statement.close();} catch (SQLException logOrIgnore) {}if (connection != null) try { connection.close();} catch (SQLException logOrIgnore) {}}返回行；}

控制器(servlet):

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {尝试 {列表<行>行 = someDAO.list();request.setAttribute("行", 行);} catch (SQLException e) {request.setAttribute("error", "检索行失败.");e.printStackTrace();}request.getRequestDispatcher("page.jsp").forward(request, response);}

视图(page.jsp):

<c:out value="${row.name}"/>...</c:forEach><c:if test="${not empty error}">错误:${error}</c:if>

I'd like to swap out an sql:query for some Java code that builds a complex query with several parameters. The current sql is a simple select.

<sql:query
   var="result"
   dataSource="${dSource}"
   sql="select * from TABLE ">
</sql:query>

How do I take my Java ResultSet (ie. rs = stmt.executeQuery(sql);) and make the results available in my JSP so I can do this textbook JSP?

To be more clear, I want to remove the above query and replace it with Java.

<%
  ResultSet rs = stmt.executeQuery(sql); // Messy code will be in some Controller
%>

<c:forEach var="row" items="${result.rows}">
  <c:out value="${row.name}"/>
</c:forEach>

Do I set the session/page variable in the Java section or is there some EL trick that I can use to access the variable?

解决方案

Model (Row):

public class Row { 
    private String name;
    // Add/generate constructor(s), getters and setters.
}

DAO:

public List<Row> list() throws SQLException {
    Connection connection = null;
    Statement statement = null;
    ResultSet resultSet = null;
    List<Row> rows = new ArrayList<Row>();

    try {
        connection = database.getConnection();
        statement = connection.createStatement();
        resultSet = statement.executeQuery(SQL_LIST);
        while (resultSet.next()) {
            Row row = new Row();
            row.setName(resultSet.getString("name"));
            // ...
            rows.add(row);
        }
    } finally {
        if (resultSet != null) try { resultSet.close(); } catch (SQLException logOrIgnore) {}
        if (statement != null) try { statement.close(); } catch (SQLException logOrIgnore) {}
        if (connection != null) try { connection.close(); } catch (SQLException logOrIgnore) {}
    }

    return rows;
}

Controller (servlet):

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try {
        List<Row> rows = someDAO.list();
        request.setAttribute("rows", rows);
    } catch (SQLException e) {
        request.setAttribute("error", "Retrieving rows failed.");
        e.printStackTrace();
    }
    request.getRequestDispatcher("page.jsp").forward(request, response);
}

View (page.jsp):

<c:forEach items="${rows}" var="row">
    <c:out value="${row.name}" />
    ...
</c:forEach>
<c:if test="${not empty error}">Error: ${error}</c:if>

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