请求处理失败;嵌套异常是java.lang.NullPointerException

时间：2013-05-12 05:50:42

标签： spring hibernate spring-mvc

我创建了一个表单并且在帖子上我想将这些值保存到数据库并在页面上显示保存的值 我是初学mvc的新手，因此我不知道我哪里出错了。

这是StackTrace - 

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:894)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)


 root cause 

java.lang.NullPointerException
com.projects.data.HomeController.addCustomer(HomeController.java:36)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:601)
org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)


note The full stack trace of the root cause is available in the VMware vFabric tc Runtime 2.7.2.RELEASE/7.0.30.A.RELEASE logs.

模型类

package com.projects.model;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="customer")
public class Customer {

@Id
int custid;
String name;
int age;

public Customer()
{}
public Customer(int custid,String name,int age)
{
    this.custid=custid;
    this.name=name;
    this.age=age;
}

//Getters And Setters

public int getCustid() {
    return custid;
}

public void setCustid(int custid) {
    this.custid = custid;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public int getAge() {
    return age;
}

public void setAge(int age) {
    this.age = age;
}

}

Dao Class 

package com.projects.model;


import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import com.projects.model.Customer;

@Repository
public class CustomerDao {

@Autowired
private SessionFactory sessionfactory;

public SessionFactory getSessionfactory() {
    return sessionfactory;
}

public void setSessionfactory(SessionFactory sessionfactory) {
    this.sessionfactory = sessionfactory;
}

public int save(Customer customer)
{
  return (Integer) sessionfactory.getCurrentSession().save(customer);
}


 }

servlet的context.xml中

 <?xml version="1.0" encoding="UTF-8"?>
 <beans:beans xmlns="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

<!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->

<!-- Enables the Spring MVC @Controller programming model -->
<annotation-driven />

<!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
<resources mapping="/resources/**" location="/resources/" />

<!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
<beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <beans:property name="prefix" value="/WEB-INF/views/" />
    <beans:property name="suffix" value=".jsp" />
</beans:bean>

<context:component-scan base-package="com.projects.model" />

<beans:bean id="dataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">

    <beans:property name="driverClassName" value="com.mysql.jdbc.Driver" />
    <beans:property name="url" value="jdbc:mysql://localhost:3306/customerdb" />
    <beans:property name="username" value="root" />
    <beans:property name="password" value="root" />
</beans:bean>

 <beans:bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <beans:property name="dataSource" ref="dataSource" />
    <beans:property name="packagesToScan" value="com.projects.model" />

    <beans:property name="hibernateProperties">
        <beans:props>
            <beans:prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</beans:prop>
            <beans:prop key="hibernate.show_sql">true</beans:prop>
        </beans:props>
    </beans:property>

    </beans:bean>


<beans:bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
    <beans:property name="sessionFactory" ref="sessionFactory" />
</beans:bean>

 </beans:beans>

控制器类

package com.projects.model;

import java.text.DateFormat;
import java.util.Date;
import java.util.Locale;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.ui.ModelMap;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.projects.model.CustomerDao;
import com.projects.model.Customer;

/**
* Handles requests for the application home page.
*/
@Controller
public class HomeController {

private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

/**
 * Simply selects the home view to render by returning its name.
 */

private CustomerDao dao;


@RequestMapping(value = "/", method = RequestMethod.GET)        
public String customer(Locale locale, Model model) {
    logger.info("Welcome home! The client locale is {}.", locale);
    Customer customer=new Customer();
    model.addAttribute(customer);
    return "home";
}

@RequestMapping(value = "/customer", method = RequestMethod.POST)
  public String addCustomer(@ModelAttribute("customer") Customer customer, ModelMap model) {

    model.addAttribute("custid", customer.getCustid());
    model.addAttribute("name",customer.getName());
    model.addAttribute("age", customer.getAge());
    dao.save(customer);
    return "customer/customer";
}      

}

查看文件

//针对home.jsp 

  <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
  <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

 <%@ page session="false" %>
 <html>
 <head>
<title>Home</title>
 </head>
 <body>


<form:form action="${customer}" method="post" modelAttribute="customer">
<form:label path="custid">Id:</form:label>
<form:input path="custId"/> <br>

<form:label path="name">Name:</form:label>
<form:input path="name"/> <br>

<form:label path="age">Age:</form:label>
<form:input path="age"/> <br>

<input type="submit" value="Save"/>

// customer.jsp 

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Submitted Information</title>
</head>
<body>

<h2>Submitted Information</h2>
<table>
<tr>
    <td>Cust id</td>
    <td>${custid}</td>
</tr>
<tr>
    <td>Name</td>
    <td>${name}</td>
</tr>
<tr>
    <td>Age</td>
    <td>${age}</td>
</tr>
</table>
</body>
</html>

点击保存按钮后，我得到上述错误。请帮我解决此问题。

2 个答案:

答案 0 :(得分：0)

似乎是您表单中的问题。至少，必须为输入赋予名称属性：

 <form method="post" action="<c:url value='/customer/'/>">
     Cust_Id :
     <input type="text" name="custid">
     <br>

     Name :
     <input type="text" name="name">
     <br>

     Age :
     <input type="text" name="age">

     <input type="submit" value="Save">
 </form>

但是因为你使用Spring，所以最好使用Spring表单（以及spring url）：

<spring:url var="customer" value="/customer"/>
<form:form action="${customer}" method="post" modelAttribute="customer">
    <form:label path="custid">Id:</form:label>
    <form:input path="custId"/> <br>

    <form:label path="name">Name:</form:label>
    <form:input path="name"/> <br>

    <form:label path="age">Age:</form:label>
    <form:input path="age"/> <br>

    <input type="submit" value="Save"/>    
</form:form>

修改 你应该初始化dao！

@Autowired
private CustomerDao dao;

答案 1 :(得分：0)

模型的属性已用@ModelAttribute注释为可空。这样，以便在绑定期间发生异常时，有一些返回值。

请注意模型属性和模型属性参数之间的区别。

绑定和验证期间的异常可能是在整数字段中传递文本。

例外：

org.springframework.web.util.NestedServletException: 
Request processing failed; nested exception is java.lang.NullPointerException: 
Parameter specified as non-null is null: method yourMethod, parameter yourParam

在科特林

避免从student: Student到student: Student?异常。

@RequestMapping("/processFormRegister") 
fun processFormRegister(
        @Valid @ModelAttribute("firstStudent") student: Student?,
        validationResult: BindingResult
): String {
    return if (validationResult.hasErrors()) {
        "StudentFormRegister"
    } else {
        "ResultFormRegister"
    }
}

还要查看异常已转换为验证，您可以使用Hibernate Validator中的@Valid和Binding Result获得：

failed to convert value of type java.lang.string[] to required type java.lang.integer; nested exception is java.lang.numberformatexception: for input string: "a"

GL

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