java - 数据源在 struts 中不工作

Question

我尝试使用 struts 中的数据源从表中获取一些值，但它给出了异常:

类型异常报告

消息

描述服务器遇到内部错误()，导致其无法完成此请求。

异常

javax.servlet.ServletException: java.lang.NullPointerException
 org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:520)
 org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:427)
 org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
 org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
 org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)


root cause 

java.lang.NullPointerException
 login.LoginAction.execute(LoginAction.java:31)
 org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
 org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
 org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
 org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

注意 Apache Tomcat/6.0.26 日志中提供了根本原因的完整堆栈跟踪。

我的 struts-config.xml 包含数据源连接属性:

<form-beans>
    <form-bean name="LoginForm" type="login.LoginForm"/>
    <form-bean name="dynaActionForm" type="org.apache.struts.action.DynaActionForm">
        <form-property name="fname" type="java.lang.String"/>
        <form-property name="lname" type="java.lang.String"/>
    </form-bean>
</form-beans>
<data-sources>
    <data-source key="dataSource"  type="org.apache.tomcat.dbcp.dbcp.BasicDataSource">
        <set-property property="driverClassName" value="com.microsoft.sqlserver.jdbc.SQLServerDriver"/>
        <set-property property="url" value="jdbc:sqlserver://192.168.1.169:1433;databaseName=localDB"/>
        <set-property property="username" value="sa"/>
        <set-property property="password" value="pass"/>
    </data-source>
</data-sources>

<global-exceptions></global-exceptions>

<global-forwards>
    <forward name="welcome"  path="/Welcome.do"/>
</global-forwards>

<action-mappings>
    <action name="LoginForm" path="/login" scope="request" type="login.LoginAction" validate="false">
        <forward name="failure" path="/login.jsp"/>
        <forward name="success" path="/WEB-INF/success.jsp"/>
    </action>

    <action name="dynaActionForm" path="/dyna" scope="request" type="DaynaAction.dynaActionClass" validate="false">
        <forward name="filure" path="/index.jsp"/>
        <forward name="success" path="/WEB-INF/JSP/SuccessDyna.jsp"/>
    </action>

    <action path="/Welcome" forward="/welcomeStruts.jsp"/>
</action-mappings>

<controller processorClass="org.apache.struts.tiles.TilesRequestProcessor"/>

<message-resources parameter="com/myapp/struts/ApplicationResource"/>

<!-- ========================= Tiles plugin ===============================-->
<!--
This plugin initialize Tiles definition factory. This later can takes some
parameters explained here after. The plugin first read parameters from
web.xml, thenoverload them with parameters defined here. All parameters
are optional.
The plugin should be declared in each struts-config file.
- definitions-config: (optional)
Specify configuration file names. There can be several comma
separated file names (default: ?? )
- moduleAware: (optional - struts1.1)
Specify if the Tiles definition factory is module aware. If true
(default), there will be one factory for each Struts module.
If false, there will be one common factory for all module. In this
later case, it is still needed to declare one plugin per module.
The factory will be initialized with parameters found in the first
initialized plugin (generally the one associated with the default
module).
true : One factory per module. (default)
false : one single shared factory for all modules
- definitions-parser-validate: (optional)
Specify if xml parser should validate the Tiles configuration file.
true : validate. DTD should be specified in file header (default)
false : no validation

Paths found in Tiles definitions are relative to the main context.
-->
<plug-in className="org.apache.struts.tiles.TilesPlugin" >
    <set-property property="definitions-config" value="/WEB-INF/tiles-defs.xml" />
    <set-property property="moduleAware" value="true" />
</plug-in>

<!-- ========================= Validator plugin ================================= -->
<plug-in className="org.apache.struts.validator.ValidatorPlugIn">
    <set-property
        property="pathnames"
        value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml"/>
</plug-in>

我的 Action 类是

package login;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import java.util.*;
import javax.sql.DataSource;

public class LoginAction extends org.apache.struts.action.Action {

    /* forward name="success" path="" */
    private static final String SUCCESS = "success";
    private final static String FAILURE = "failure";
    private ResultSet rs;
    private PreparedStatement ps;
    private Connection conn;

    @Override
    public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        LoginForm formBean = (LoginForm) form;
        String fname = formBean.getName();
        String lname = formBean.getEmail();
        if ((fname == null) || lname == null) {
            ArrayList al = new ArrayList();
            DataSource ds = (DataSource) servlet.getServletContext().getAttribute("");
            conn = ds.getConnection();
            String query = "select * from login";
            ps = conn.prepareStatement(query);
            ResultSet rs = ps.executeQuery();
            int i = 1;
            while (rs.next()) {
                al.add(rs.getString(i));
                al.add(rs.getString(i + 1));
                i++;
            }
            request.setAttribute("value", al);
            formBean.setError();
            return mapping.findForward(FAILURE);
        }
        return mapping.findForward(SUCCESS);
    }
}

请任何人帮助运行上述程序......

问候 穆利V

Answer 1

您的DataSource 为null，这会导致NullPointerException。它是 null 因为你试图获取一个不存在的属性:

DataSource ds = (DataSource) servlet.getServletContext().getAttribute("");

看来在 Struts 中您可以通过调用 getDataSource(request) 来获取 DataSource

另一件事 - 您已经标记了 struts2，但正在使用 struts1。您确定您使用的是正确的库吗？