SQLException：没有为参数1指定值 [英] SQLException: No value specified for parameter 1

问题描述

我在执行应用程序时遇到以下错误：

I encountered the following error when I was executing my application:

java.sql.SQLException：没有为参数1指定值

java.sql.SQLException: No value specified for parameter 1

这是什么意思？

我的 UserGroup 我的名单中的列表：

My UserGroup list in my dao:

public List<UsuariousGrupos> select(Integer var) {
    List<UsuariousGrupos> ug= null;
    try {
        conn.Connection();
        stmt = conn.getPreparedStatement("select id_usuario, id_grupo from usuarios_grupos where id_grupo ='" + var + "'");
        ResultSet rs = stmt.executeQuery();
        ug = new ArrayList<UsuariousGrupos>();
        while (rs.next()) {
            ug.add(getUserGrupos(rs));
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        conn.Disconnected();
    }
    return ug;
}

public UsuariousGrupos getUserGrupos(ResultSet rs) {
    try {
        UsuariousGrupos ug = new UsuariousGrupos(rs.getInt("id_usuario"), rs.getInt("id_grupo"));
        return ug;
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return null;
}

我的托管bean中用户组的获取列表：

My get list of User groups in my managed bean:

public List<UsuariousGrupos> getListOfUserGroups() {
    List<UsuariousGrupos> usuariosGruposList = userGrpDAO.select(var2);
    listOfUserGroups = usuariosGruposList;
    return listOfUserGroups;
}

我的JSF页面：

 <p:dataTable var="usergroups" value="#{usuariousGruposBean.listOfUserGroups}">
     <p:column headerText="" style="height: 0" rendered="false">
         <h:outputText value="#{usergroups.id_grupo}"/>
     </p:column>

我的数据表能够显示数据库中的组列表。但是，当我在数据表中选择单个行时，应用程序与我的数据库建立连接以显示所选结果需要一些时间。

My data table is able to display the list of groups from the database. However, when I select an individual row within my data table, it takes some time for the application to establish connection with my database to display the selected result.

此外，它奇怪的是，应用程序能够比其他应用程序更快地显示某些选定的结果。它与我在开头指出的异常有什么关系吗？

Also, it is weird that the application is able to display certain selected results quicker than others. Does it have anything to do with the Exception I pointed out at the beginning?

错误：

Disconnected
Connected!!
java.sql.SQLException: No value specified for parameter 1
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1075)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:929)
    at com.mysql.jdbc.PreparedStatement.checkAllParametersSet(PreparedStatement.java:2560)
    at com.mysql.jdbc.PreparedStatement.fillSendPacket(PreparedStatement.java:2536)
    at com.mysql.jdbc.PreparedStatement.fillSendPacket(PreparedStatement.java:2462)
    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2216)
    at br.dao.UsuariousGruposDAO.select(UsuariousGruposDAO.java:126)
    at br.view.UsuariousGruposBean.getListOfUserGroups(UsuariousGruposBean.java:54)


SEVERE: Error Rendering View[/index.xhtml]
javax.el.ELException: /index.xhtml @61,99 value="#{usuariousGruposBean.listOfUserGroups}": Error reading 'listOfUserGroups' on type br.view.UsuariousGruposBean
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:114)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182)

推荐答案

没有 Connection（）和<$ c这样的方法$ c> getPreparedStatement（） on java.sql.Connection 。

There is no such method as Connection() and getPreparedStatement() on java.sql.Connection.

conn.Connection();
stmt = conn.getPreparedStatement("select id_usuario, id_grupo from usuarios_grupos where id_grupo ='" + var + "'");

conn 显然是一个本土的包装纸JDBC代码。您的特定问题可能是由 getPreparedStatement（）方法背后的代码引起的。在委派给 real ？附加到SQL字符串中javase / 6 / docs / api / java / sql / Connection.html＃prepareStatement％28java.lang.String％29rel =nofollow noreferrer> connection.prepareStatement（） 方法。

The conn is clearly a homegrown wrapper around JDBC code. Your particular problem is likely caused by the code behind the getPreparedStatement() method. It's apparently appending a ? to the SQL string before delegating through to the real connection.prepareStatement() method.

您可能不想听到这个，但您的JDBC方法完全被破坏了。此设计表明JDBC Connection 是作为静态或实例变量保存的，它是 threadunsafe 。

You probably don't want to hear this, but your JDBC approach is totally broken. This design indicates that the JDBC Connection is hold as a static or instance variable which is threadunsafe.

您需要完全重写它，以便归结为以下正确用法和变量范围：

You need to totally rewrite it so that it boils down to the following proper usage and variable scoping:

public List<UsuariousGrupos> select(Integer idGrupo) throws SQLException {
    Connection connection = null;
    PreparedStatement statement = null;
    ResultSet resultSet = null;
    List<UsuariousGrupos> usuariousGrupos = new ArrayList<UsariousGrupos>();

    try {
        connection = database.getConnection();
        statement = connection.prepareStatement("select id_usuario, id_grupo from usuarios_grupos where id_grupo = ?");
        statement.setInt(1, idGrupo);
        resultSet = statement.executeQuery();

        while (resultSet.next()) {
            usuariousGrupos.add(mapUsuariousGrupos(resultSet));
        }
    } finally {
        if (resultSet != null) try { resultSet.close(); } catch (SQLException ignore) {}
        if (statement != null) try { statement.close(); } catch (SQLException ignore) {}
        if (connection != null) try { connection.close(); } catch (SQLException ignore) {}

    }

    return usuariousGrupos;
}

另请参阅：

• 如何在Java中声明一个全局静态类？



See also:

• How to declare a global static class in Java?

对于具体问题没有相关性，你还有另一个问题。以下异常

Unrelated to the concrete question, you've another problem. The following exception




javax.el.E​​LException：/index.xhtml @ 61,99 value =＃{usuariousGruposBean.listOfUserGroups}：在类型br.view.UsuariousGruposBean上读取'listOfUserGroups'时出错

javax.el.ELException: /index.xhtml @61,99 value="#{usuariousGruposBean.listOfUserGroups}": Error reading 'listOfUserGroups' on type br.view.UsuariousGruposBean

表示您正在 getter中执行JDBC内容方法而不是（post）构造函数或（action）侦听器方法。这也是一个非常糟糕的主意，因为在渲染响应期间可以多次调用getter。相应修复。

indicates that you're doing the JDBC stuff inside a getter method instead of (post)constructor or (action)listener method. This is also a very bad idea because a getter can be called more than once during render response. Fix it accordingly.



• 为什么JSF多次调用getter


• Why JSF calls getters multiple times

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