SpringMVC+JdbcTemplate报空指针异常

[一只小菜鸟1992]

使用SpringMVC+JdbcTemplate查询报空指针异常：
各配置情况如下：

web.xml:
<display-name>StudyJDBC</display-name>
<servlet>
<servlet-name>jdbc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>jdbc</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>



spring-mvc:
<!-- 配置HandlerMapping -->
<mvc:annotation-driven></mvc:annotation-driven>
<!-- 打开扫描 -->
<context:component-scan base-package="com.jdbc"></context:component-scan>
<!-- 配置ViewResolver -->
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/"></property>
<property name="suffix" value=".jsp"></property>
</bean>


applicationContext.xml
<!-- 配置Spring JDBC -->
<!-- 打开扫描-->
<context:component-scan base-package="com.jdbc.dao"></context:component-scan>
<bean id="template" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="DataSource" ref="dbcp"></property>
</bean>
<!-- 配置连接池对象，用于注入到jdbcTemplate里 -->
<bean id="dbcp" class="org.apache.commons.dbcp.BasicDataSource">
<property name="url" value="jdbc:mysql://localhost:3306/test"></property>
<property name="username" value="root"></property>
<property name="password" value="123456"></property>
<property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
</bean>


CostRowMapper:
import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.jdbc.core.RowMapper;

public class CostRowMapper implements RowMapper<Cost>{

@Override
public Cost mapRow(ResultSet rs, int index) throws SQLException {
Cost c=new Cost();
c.setName(rs.getString("name"));
c.setBase_cost(rs.getDouble("base_cost"));
c.setBase_duration(rs.getLong("base_duration"));
c.setCost_id(rs.getInt("cost_id"));
c.setCost_type(rs.getString("cost_type"));
c.setCreatime(rs.getDate("creatime"));
c.setDescr(rs.getString("descr"));
c.setStartmie(rs.getDate("startime"));
c.setStatus(rs.getString("status"));
c.setUnit_cost(rs.getDouble("unit_cost"));
return c;
}

}


cost:
private Integer cost_id;//资费ID
private String name;//资费名称
private Long base_duration;//基本时长
private Double base_cost;//基本费用
private Double unit_cost;//单位费用
private String status;//状态
private String descr;//描述
private Date creatime;//创建时间
private Date startmie;//生效时间
private String cost_type;//消费类型


cost:Dao:
import java.util.List;

import javax.annotation.Resource;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository()
public class CostDao {
@Resource
private JdbcTemplate template;
public List<Cost> findAll(){
String sql="select * from cost";
CostRowMapper cr=new CostRowMapper();
List<Cost> costs=template.query(sql, cr);
System.out.println(123);
System.out .println(template);
return costs;
}
}


Controller:
import java.util.List;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;

import com.dao.Cost;
import com.dao.CostDao;


@Controller
public class CostController {


@RequestMapping("cost.do")
public String find(ModelMap model){
CostDao cd=new CostDao();
List<Cost> costs=cd.findAll();
System.out.println(cd);
model.put("costs", costs);
return "showCost";
}
}


运行报的异常：
严重: Servlet.service() for servlet [jdbc] in context with path [/StudyJDBC] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at com.dao.CostDao.findAll(CostDao.java:18)
at com.jdbc.day06.CostController.find(CostController.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:953)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:844)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:829)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1083)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:640)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2517)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2506)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)


若将costDao换成注入方式，
private CostDao costDao
编译都不会通过

[一只小菜鸟1992]

请大神解救，困扰好久了

[一只小菜鸟1992]

解决了。知道问题出在哪了。costDao不能是new出来的。必须要通过 ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml"); CostDao cd=ac.getBean("costDao",CostDao.class"); 获得 否则JdbcTemplate的值为null