配置了DAO，似乎甚至没有进入旨在使用DAO的调用类内部的finder方法。

/src/main/resources/database-config.xml：

<bean id="dataSourceProducts" class="org.apache.commons.dbcp2.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="${db.driver}" />
    <property name="url" value="${db.urlProducts}" />
    <property name="username" value="${db.username}" />
    <property name="password" value="${db.password}" />
    <property name="initialSize" value="${db.initialSize}"/>
    <property name="maxTotal" value="${db.maxTotal}"/>
    <property name="maxIdle" value="0"/>
    <property name="minIdle" value="0"/>
    <property name="maxWaitMillis" value="10000"/>
    <property name="validationQuery" value="SELECT NOW();"/>
    <property name="timeBetweenEvictionRunsMillis" value="10000"/>      
    <property name="removeAbandonedOnMaintenance" value="true"/>
    <property name="maxConnLifetimeMillis" value="10000"/>
    <property name="minEvictableIdleTimeMillis" value="1000"/>

/src/main/webapp/WEB-INF/mvc-dispatcher-servlet.xml：

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:util="http://www.springframework.org/schema/util"
    xmlns:cache="http://www.springframework.org/schema/cache"
    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.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/cache
        http://www.springframework.org/schema/cache/spring-cache.xsd
        http://www.springframework.org/schema/util 
        http://www.springframework.org/schema/util/spring-util.xsd">

    <import resource="classpath:database-config.xml" />

    <context:component-scan base-package="com.myapp.dao,com.myapp.manager" />

    <mvc:annotation-driven />

/src/main/java/com/myapp/dao/ProductDao.java：

package com.myapp.dao;

@Repository
public class ProductDao {

    public JdbcTemplate jdbcTemplateProduct = null;

    @Autowired  
    @Qualifier("dataSourceProducts")
    DataSource dataSourceProducts;

    ProductDao() { }

    /**
     * constructor to create object and to use for test cases class. 
     * @param jdbcTemplateObject
     */
    @VisibleForTesting
    public ProductDao(JdbcTemplate jdbcTemplateObject) {
        this.jdbcTemplateProduct = jdbcTemplateObject;
    }

    @PostConstruct
    public void init() {
        jdbcTemplateProduct = new JdbcTemplate(dataSourceProducts); 
    }   

    public boolean runValidationQuery() {
        boolean retValue = false;
        SqlRowSet rst = null;
        rst = jdbcTemplateProduct.queryForRowSet("select now()");
        if (rst != null) {
            retValue = true;
        }
        return retValue;
    }
}

/ src / main / java / com / myapp / manager / ProductManager：

package com.myapp.manager;

@Controller
public class ProductManager {

    @Autowired
    ProductDao productDao;

    boolean checkValue = false;

    public void check() throws IOException {
        checkValue = productDao.runValidationQuery();
    }

    public static void main(String args []) {
        ProductManager productManager = new ProductManager();
        productManager.check();
    }
 }

当main（）方法进入时，这会不断抛出NullPointerException

productManager.check();

甚至无法进入productManager.check();

同一个NPE马上出现：

Exception in thread "main" java.lang.NullPointerException
    at com.myapp.manager.ProductManager.check(ProductManager.java:12)
    at com.myapp.manager.ProductManager.main(ProductManager.java:17)

遵循此项目中其他DAO的这种模式，但不了解当前的问题是什么？

是否怀疑其配置问题或缺少注释问题？

尝试执行Spring JDBC查询时获取NPE

配置了DAO，似乎甚至没有进入旨在使用DAO的调用类内部的finder方法。

0 个答案: