NPE 在我的服役 class 中使用球衣 spring

Question

我是 spring 的新手，其余的我还在学习中。我在通过客户端从休息 api 调用资源时遇到问题。

我的数据库中有一些数据，我正在使用 spring 注入值并获得连接。

当我从客户端发出 GET 请求时，我收到了 NPE。

下面是我的 DAO Class

public interface CustomerDao {

public List<Customer> getCustomersDao();

}

DAOImpl

public class CustomerDaoImpl implements CustomerDao {

private JdbcTemplate template;

@Autowired
public void setTemplate(JdbcTemplate template) {
    this.template = template;
}

public List<Customer> getCustomersDao() {
    return template.query("SELECT * FROM books.customers", new RowMapper<Customer>() {
        @Override
        public Customer mapRow(ResultSet rs, int rownumber) throws SQLException {
            Customer e = new Customer();
            e.setId(rs.getString(1));
            e.setName(rs.getString(2));
            e.setAge(rs.getString(3));
            return e;
        }
    });
}

服务class

public class CustomerService {

@Autowired
CustomerDao customersConnection;

public List<Customer> getAllCustomers() {

    return new ArrayList<Customer>(customersConnection.getCustomersDao());

}

资源

@Path("/persons")
public class CustomerResource {

@Autowired
CustomerService customerService;

@GET
@Produces(MediaType.APPLICATION_JSON)
public List<Customer> getAllCustomers {

    return customerService.getAllCustomers();

}

}

我的bean.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:context="http://www.springframework.org/schema/context"   
xsi:schemaLocation="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-4.0.xsd">

<context:component-scan base-package="com.sumanth.customers" />

<bean id="ds"   class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver" />
    <property name="url" value="--:--://----/---" />
    <property name="username" value="----" />
    <property name="password" value="-----" />
</bean>

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
    <property name="dataSource" ref="ds"></property>
</bean>

<bean id="customerService" class="com.sumanth.customer.db.CustomerDaoImpl">
    <property name="template" ref="jdbcTemplate"></property>
</bean>

</beans>

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet>

    <servlet-name>Jersey Web Application</servlet-name>

    <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>

    <init-param>
        <param-name>jersey.config.server.provider.packages</param-name>
        <param-value>com.sumanth.customer</param-value>
    </init-param>

    <init-param>
        <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
        <param-value>true</param-value>
    </init-param>

    <load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>
    <servlet-name>Jersey Web Application</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

</web-app>

错误：

Caused by: java.lang.NullPointerException
at com.sumanth.customer.resource.CustomerResource.getAllCustomers(CustomerResource.java:23) 
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)

第 23 行错误：

return customerService.getAllCustomers();

我使用@Autowired 连接 beans.I 知道我在连接它们时犯了一个错误任何人都可以帮助我吗

谢谢

Answer 1

我对网络 xml 和我的 bean.xml

做了一些修改

<listener>
    <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>WEB-INF/bean.xml</param-value>
</context-param>

修改了我的服务class

   @Component annotation in my service class

我的bean.xml添加了以下内容

<context:annotation-config />

我的 Impl class.I 在我的 class

上方添加了注释

@Repository("customerService")

NPE 在我的服役 class 中使用球衣 spring

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