java-Spring dataSource返回null
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我正在尝试将MySQL数据库与Spring连接.我也想将DataSource setter方法与@Autowired一起使用.每次运行代码时,DataSource始终返回null.
错误：
HTTP Status 500 - Request processing failed; nested exception is java.lang.NullPointerException
有人可以告诉我我的代码有什么问题吗？请在下面找到我的代码.
CustomerController.java
package com.springapp.controller;
import com.springapp.beans.Customer;
import com.springapp.service.CustomerService;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class CustomerController {
private CustomerService customerService;
@RequestMapping(value = "/", method = RequestMethod.GET)
public ModelAndView index() {
ModelAndView mv = new ModelAndView("index");
return mv;
}
@RequestMapping(value = "/listCustomers", method = RequestMethod.GET)
public ModelAndView ListCustomer() {
ModelAndView mv = new ModelAndView("customers");
Customer customer = customerService.findCustomerById(1);
mv.addObject("customer", customer);
return mv;
}
}
客户.java
package com.springapp.beans;
public class Customer {
private int id;
private String firstName;
private String lastName;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
}
CustomerDAO.java
package com.springapp.dao;
import com.springapp.beans.Customer;
public interface CustomerDAO {
public Customer findCustomerById(int customerId);
}
客户服务
package com.springapp.service;
import com.springapp.beans.Customer;
import com.springapp.dao.CustomerDAO;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.sql.DataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
@Repository
public class CustomerService implements CustomerDAO {
private DataSource dataSource;
@Autowired
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
@Override
public Customer findCustomerById(int customerId) {
String sql = "SELECT * FROM CUSTOMER WHERE CUST_ID = 1";
Customer customer = new Customer();
Connection conn = null;
try {
conn = dataSource.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
ResultSet rs = ps.executeQuery();
if (rs.next()) {
customer.setFirstName(rs.getString("first_name"));
customer.setLastName(rs.getString("last_name"));
}
rs.close();
ps.close();
return customer;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
applicationContext.xml
<?xml version='1.0' encoding='UTF-8' ?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost/testjavadb" />
<property name="username" value="root" />
<property name="password" value="" />
</bean>
</beans>
dispatcher-servlet.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
<context:component-scan base-package="com.springapp" />
<mvc:annotation-driven />
<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>
错误记录
HTTP状态500-请求处理失败；嵌套的异常是java.lang.NullPointerException
类型例外报告
message Request processing failed; nested exception is java.lang.NullPointerException
描述服务器遇到内部错误,导致服务器无法满足此请求.
例外
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:973)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
java.lang.NullPointerException
com.springapp.controller.CustomerController.ListCustomer(CustomerController.java:28)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:497)
org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:214)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:690)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.54 logs.
解决方法:
在您的CustomerController类中,尝试更改此行：
private CustomerService customerService;
至：
@Autowired
private CustomerService customerService;
或者,您也可以根据需要通过设置器或构造函数注入对其进行自动布线.
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