Java JdbcTemplate 空指针异常
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JdbcTemplate NullPointerException
提问by Tom Joad
I am trying to save data to database with Spring's JdbcTemplate, but I get this error message. If I do it normal way with PreparedStatements it's working.
我正在尝试使用 Spring 的 JdbcTemplate 将数据保存到数据库，但收到此错误消息。如果我使用 PreparedStatements 以正常方式进行操作，则它可以正常工作。
My CarDAO class:
我的 CarDAO 类：
@Repository
@Service
public class CarDAO implements CarDAOService {
private JdbcTemplate jdbcTemplate;
public JdbcTemplate getJdbcTemplate() {
return jdbcTemplate;
}
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
public void saveCarToDB(CarBean carbean) {
final String sql = "insert into car (make, model) values (?,?)";
Object[] parameters = new Object[] {carbean.getMake()+
carbean.getModel()};
//if I do here system.out.print(Arrays.toString(parameters));
//it will print right make/model.
jdbcTemplate.update(sql, parameters);
//console says it is that row above, but I don't get how. Both parameters has values?
//WARNING: StandardWrapperValve[spring-dispatcher]: Servlet.service() for servlet
//springdispatcher threw exception
}
Spring-base.xml
Spring-base.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:mvc="http://www.springframework.org/schema/mvc"
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="bean, dao" />
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/Jsp/" />
<property name="suffix" value=".jsp" />
</bean>
<!-- DATA SOURCE -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="org.mariadb.jdbc.Driver" />
<property name="url" value="jdbc:mariadb://XXXXX" />
<property name="username" value="XXXXX" />
<property name="password" value="XXXXX" />
<property name="initialSize" value="1" />
<property name="maxActive" value="5" />
</bean>
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
<mvc:annotation-driven />
</beans>
I didn't include my Controller or CarDAOService class, because I think the problem isn't there. They are forwarding right parameters to CarDAO class.
我没有包含我的 Controller 或 CarDAOService 类，因为我认为问题不存在。他们将正确的参数转发给 CarDAO 类。
采纳答案by GriffeyDog
You need to put the @Autowiredannotation on your setter:
您需要将@Autowired注释放在您的 setter 上：
@Autowired
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
回答by Sireesh Yarlagadda
Autowired bean via @Autowired, and it can be applied on setter method, constructor or a field.
通过@Autowired 自动装配 bean，它可以应用于 setter 方法、构造函数或字段。
Try this
尝试这个
@Autowired
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
