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：

输入例外报告

消息

description服务器遇到内部错误（），导致无法完成此请求。

例外

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datasources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.....

此致 Mouli V

Answer 1

DataSource为null，导致NullPointerException。它是null因为你试图得到一个不存在的属性：

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

在Struts中，您可以通过调用getDataSource(request)

获取DataSource

另一件事 - 你已经标记了struts2，但是使用了struts1。您确定使用的是正确的库吗？

Answer 2

当您使用Struts-1.X内置的“数据源”功能时，struts-config.xml包含所有与DB相关的详细信息。您可以使用“validationQuery”属性来验证有关db-connection的所有信息。

 <data-sources> 
    <data-source key="datasource" type="org.apache.tomcat.dbcp.dbcp.BasicDataSource"> 
      <set-property property="password" value="pass" /> 
      <set-property property="username" value="uname" /> 
      <set-property property="driverClassName" value="oracle.jdbc.driver.OracleDriver" /> 
      <set-property property="url" value="jdbc:oracle:thin:@localhost:1521:abc" /> 
      <set-property property="validationQuery" value="select sysdate from dual" />    
    </data-source> 
 </data-sources>

Strtus将初始化并提供Datasource，我们可以通过以下方式在任何Action类中使用它：

public class LoginAction extends Action
{
   public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
   {

      LoginForm loginForm = (LoginForm) form;
      if (loginForm.getUsername() != null && loginForm.getPassword() != null)
      {

DataSource dataSource = getDataSource(request, "datasource");
Connection myConnection = dataSource.getConnection();
PreparedStatement stmt = null;
String select = "SELECT USERNAME,PASSWORD from USER where USERNAME=?";
stmt = myConnection.prepareStatement(select);
stmt.setString(1, username);
rst = stmt.executeQuery();

................
}
}

数据源在struts中不起作用

2 个答案: