java数据源在struts中不起作用

3 月 Questions & Answers 4292

我试图使用struts中的datasource从表中获取一些值，但它给出了一个例外：

类型异常报告

信息

说明服务器遇到内部错误（），无法完成此请求

例外情况

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，根本原因的完整堆栈跟踪可在Apache Tomcat/6.0.26日志中找到

还有我的struts配置。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>

我的动作课是

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

问候莫利五世

共 (2) 个答案

# 1 楼答案

当您使用Struts-1时。X内置“数据源”功能，struts配置。xml包含所有与数据库相关的详细信息。因为您可以使用“validationQuery”属性来验证关于db连接的所有内容

 <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>

STRTU将初始化并提供数据源，我们可以通过以下方式在任何操作类中使用它：

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();

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

# 2 楼答案
你的DataSource是null，这会导致NullPointerException。这是null，因为您试图获取一个不存在的属性：
```
DataSource ds = (DataSource) servlet.getServletContext().getAttribute("");
```
在Struts中，似乎可以通过调用^{}来获得DataSource

另一件事——你已经标记了struts2，但是正在使用struts1。您确定使用了正确的库吗

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有 Java 编程相关的问题?

java数据源在struts中不起作用

共 (2) 个答案

# 1 楼答案

# 2 楼答案