javax.servlet.ServletException:实例化servlet类org.server.db.test.ServletExample时出错_Java_Hibernate_Servlets

javax.servlet.ServletException:实例化servlet类org.server.db.test.ServletExample时出错

java hibernate servlets

javax.servlet.ServletException:实例化servlet类org.server.db.test.ServletExample时出错,java,hibernate,servlets,Java,Hibernate,Servlets,我刚开始学习Hibernate和servlet。我有一个表单（姓名、电子邮件），我填写这些字段，请求就会发送到服务器。然后我从服务器获取数据并打印它们。这是正确的 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("userNam

我刚开始学习Hibernate和servlet。我有一个表单（姓名、电子邮件），我填写这些字段，请求就会发送到服务器。然后我从服务器获取数据并打印它们。这是正确的

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String name = request.getParameter("userName");
    String email = request.getParameter("email");
    String ip = request.getRemoteAddr();

    response.getWriter().println("<html>");
    response.getWriter().println("<head>");
    response.getWriter().println("<title>This is a response</title>");
    response.getWriter().println("<head>");
    response.getWriter().println("<body>");

    response.getWriter().println("<br>Your name is: " + name);
    response.getWriter().println("<br>Your email is: " + email);
    response.getWriter().println("<br>Your IP address is: " + ip);

    response.getWriter().println("</body>");
    response.getWriter().println("</html>");

}

我还有一个数据类：

@Entity
public class Data {

    @Id
    @GeneratedValue
    private int Id;
    private String userName;
    private String userEmail;

//getteres, setters...
}

但是如果我把这段代码放到Servlet中，就会得到一个HTTP错误500。我可以确定的错误消息如下：

javax.servlet.ServletException: Error instantiating servlet class org.server.db.test.ServletExample org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11P‌rotocol.java:602) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:722)

如何将我的信息从服务器放入数据库

my web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Example02</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <description></description>
    <display-name>ServletExample</display-name>
    <servlet-name>ServletExample</servlet-name>
    <servlet-class>org.server.db.test.ServletExample</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletExample</servlet-name>
    <url-pattern>/servlet1</url-pattern>
  </servlet-mapping>
</web-app>


例02
index.html
index.htm
index.jsp
default.html
default.htm
default.jsp
servlete示例
servlete示例
org.server.db.test.servlete示例
servlete示例
/servlet1

休眠cfg文件：

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.postgresql.Driver</property>
        <property name="connection.url">jdbc:postgresql://localhost:5432/db</property>
        <property name="connection.username">postgres</property>
        <property name="connection.password">***</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">2</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>

        <!-- Enable Hibernate's current session context -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create</property>

         <mapping class="org.server.db.test.Data" />
         <mapping class="org.server.db.test.ServletExample" />

    </session-factory>

</hibernate-configuration>


org.postgresql.Driver
jdbc:postgresql://localhost:5432/db
博士后
***
2.
org.hibernate.dialogue.PostgreSqlDialogue
线
org.hibernate.cache.NoCacheProvider
真的
创造

javax.servlet.ServletException:实例化servlet类org.server.db.test.ServletExample时出错

至此，在服务器的掩护下，以下构造失败，出现异常：

ServletExample servletExample = new ServletExample();

确切原因将在stacktrace中进一步提到。这是最底层的。阅读服务器日志以找到它。这个问题至少与“将数据从UI保存到数据库”无关。

看看例外情况：它肯定出现在服务器的标准错误日志文件中。例外情况可能会告诉您一个提示。如果您不能理解，请将其放在这里，我们将尝试.javax.servlet.ServletException:Error实例化servlet类org.server.db.test.ServletExample org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:102）org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:293）org.apache.coyote.http11.Http11Processor.process（Http11Processor.java:859）org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process（Http11Protocol.java:602）org.apache.tomcat.util.net.JIoEndpoint$Worker.run（JIoEndpoint.java:489）java.lang.Thread.run（Thread.java:722）……是否没有内部异常？

ServletExample servletExample = new ServletExample();