spring cloud使用JpaRepository，dao层无法注入容器，调试报空指针的解决思路

指针的解决思路"/>

spring cloud使用JpaRepository，dao层无法注入容器，调试报空指针的解决思路

     公司岗位调整，我从一个安卓开发转后台开发，以前在其他公司也接触过后台，那时公司用的是ssm框架，不过安卓还是
主业务，后台业务也只是略而兼之，并未深研，想着公司这次给机会做后台，本着技多不压身，就欣然接受，此时已经2019年了，微服务方兴未艾，如火如荼，自然我也就去学习微服务了，在学习过程中，spring cloud使用JpaRepository，编译是能通过，在调试接口时报了一个空指针，经过debug调试，是接口

public interface ProductInfoRepository extends JpaRepository<ProductInfo, String> {List<ProductInfo> findByProductStatus(List<String> productIdStatus);}

 在下面的service中

@Service
public class ProductInfoServiceImpl implements IProductInfoService {@Autowired(required = false)private ProductInfoRepository productInfoRepository;@Overridepublic List<ProductInfo> getProductList() {List<String> integerList = new ArrayList<>();integerList.add("1");List<ProductInfo> productInfoList = productInfoRepository.findByProductStatus(integerList);return productInfoList;}
}

      其中private ProductInfoRepository productInfoRepository是null的,ProductInfoRepository没有注入到容器中
调试几遍还是报空指针，只好求助百度，可以说困扰了我4天，都没有找到spring cloud使用JpaRepository报空指针的解决方案
网上找到的以下方案，都试了，都无用
1.private ProductInfoRepositoryproductInfoRepository是不是没有用@Autowired(required = false)注解，检查自己写的代码，是注解了
2.public interface ProductInfoRepository加上@Component，@Repository, 加上后，调试结果，service中的productInfoRepository还是为null,继续报空指针
3.controller和service中的方法是不是private的，检查自己的代码，方法都是public,排除该怀疑对象
4.entity实体类加上@table,@colum,调试结果，service中的productInfoRepository还是为null，报空指针
5.甚至自己怀疑是不是(required = false)了，去掉该配置，自然就报了另外一个异常，方案还是不对
6.Application上加上

@ComponentScan(basePackages = {"com.chengfeng.product.controller","com.chengfeng.product.service"}),
@EntityScan(basePackages = "com.chengfeng.product.entity")
@EnableJpaRepositories(basePackages = "com.chengfeng.product.repository")

即代码为

@SpringBootApplication（）(exclude = DataSourceAutoConfiguration.class)
@EnableDiscoveryClient
@ComponentScan(basePackages = {"com.chengfeng.product.controller","com.chengfeng.product.service"}),
@EntityScan(basePackages = "com.chengfeng.product.entity")
@EnableJpaRepositories(basePackages = "com.chengfeng.product.repository")
public class ProductApplication {public static void main(String[] args) {SpringApplication.run(ProductApplication.class, args);}}

上述加上，调试结果，service中的productInfoRepository还是为null，报空指针,
7.检查定义的entity实体类ProductInfo中的属性字段是否与数据库中一致,一一检查，都一一对应，排除该怀疑对象
8.当然什么重启了，清除缓存，说jar包冲突的，把原来的jar包全部清除重新下载，依然无用。
说实话，搞了几天都快崩溃了，放弃心又不甘，元气恢复，又鬼使神差继续调试。
9.是不是new service对象或者new  ProductInfoRepository对象了，检查自己的代码，也排除该怀疑对象
10.最后实在没有脾气了，把ProductInfoRepository定义的接口屏蔽掉，用JpaRepository原生生成的默认方法，还是报空指针。

最后，看了一眼ProductApplication 

@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
@EnableDiscoveryClient
public class ProductApplication {public static void main(String[] args) {SpringApplication.run(ProductApplication.class, args);}
}

死马当活马医，把(exclude = DataSourceAutoConfiguration.class)去掉，将原来出现的

Error creating bean with name 'entityManagerFactory' defined in class path resource[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]

异常暴露出来，把这个问题解决，看能不能顺便把空指针解决，然而运行后先报

HHH000342: Could not obtain connection to query metadata : Driver com.mysql.cj.jdbc.Driver claims to not accept jdbcUrl, 
jdbc:mysql:http://localhost:3306/product?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC

了一个新的问题，再报

 Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException:Error creating bean with name 'entityManagerFactory' defined in class path resource[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.service.spi.ServiceException:Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

 根据网上资料，application.properties中的spring.datasource.***肯定有问题，仔细看了几遍application.properties：

spring.application.name=productserver.port=8081
eureka.client.service-url.defaultZone: http://localhost:8761/eureka/spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.datasource.url= jdbc:mysql:http://localhost:3306/product?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC
spring.datasource.username = root
spring.datasource.password = 123456spring.jpa.hibernate.ddl-auto = update# 方便jpa调试的配置
spring.jpa.show-sql = true

也没发现什么问题，最后经过对比，发现jdbc:mysql后面多了个http,之前没有开发配置过数据库，也不知这里到底如何配置，什么时候这里多了个http,难道是因为多了个http,抱着疑问的态度改成

spring.datasource.url= jdbc:mysql://localhost:3306/product?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC

 奇迹出现了，项目成功运行起来，最后接口调试，service中的productInfoRepository也成功注入容器了了，接口也调通了，也不报空指针了。此刻我已经知道，肯定是ProductInfoRepository中的接口写的不符合jpa规范，所以才造成ProductInfoRepository不能成功注入容器，将原来的方法:

// List<ProductInfo> findByProductStatus(List<String> productIdStatus);

 放开，运行，果然是又报错，

@SpringBootApplication加上(exclude = DataSourceAutoConfiguration.class)，运行项目，错误消失，接口调试，继续报空指针，
至于为什么这个方法造成jpa不能注入容器，想必是这种接口定义方法不符合jpa规范，jpa识别不了。

最终，spring cloud使用jpa,要避免Repository不能注入容器，防止空指针的发生，除了排除上述10点怀疑对象，还要注意以下3点：

（1）@SpringBootApplication不能加(exclude = DataSourceAutoConfiguration.class)

（2）application.properties中关于数据库的配置一定要准确

（3）继承JpaRepository的dao层接口中自己定义的方法一定要符合jpa规范，按jpa的提示定义相关防范，不要自己随意命名，

最后附上spring cloud demo的部分

pom.xml代码

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns=".0.0" xmlns:xsi=""xsi:schemaLocation=".0.0 .0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.2.1.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.chengfeng</groupId><artifactId>product</artifactId><version>0.0.1-SNAPSHOT</version><name>product</name><description>Demo project for Spring Boot</description><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><java.version>1.8</java.version><spring-cloud.version>Hoxton.RC2</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>${spring-cloud.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build><repositories><repository><id>spring-milestones</id><name>Spring Milestones</name><url>;/url></repository></repositories></project>

application.properties代码：

spring.application.name=productserver.port=8081
eureka.client.service-url.defaultZone: http://localhost:8761/eureka/spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
spring.datasource.url= jdbc:mysql://localhost:3306/product?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=UTC
spring.datasource.username = root
spring.datasource.password = 123456spring.jpa.hibernate.ddl-auto = update# 方便jpa调试的配置
spring.jpa.show-sql = true

package com.chengfeng.product;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;@SpringBootApplication
@EnableDiscoveryClient
public class ProductApplication {public static void main(String[] args) {SpringApplication.run(ProductApplication.class, args);}}

 controller层ProductController.java代码

package com.chengfeng.product.controller;@RestController
@RequestMapping("/product")
public class ProductController {@Autowiredprivate IProductInfoService productInfoService;@GetMapping("/list")public void getProductList() {System.out.println("开始获取getProductList");//  1.查询所有商品List<ProductInfo> productInfoList = productInfoService.getProductList();System.out.println("获取的getProductList == ",productInfoList);}
}

Entity实体类ProductInfo.java代码

package com.chengfeng.product.entity;import javax.persistence.Entity;
import javax.persistence.Id;
import java.math.BigDecimal;
import java.util.Date;/*** 这里表名会自动转换，数据库中驼峰会是下划线，下面的变量也是*/@Entity
public class ProductInfo {@Idprivate String productId;/** 名字. */private String productName;/** 单价. */private BigDecimal productPrice;/** 库存. */private Integer productStock;/** 描述. */private String productDescription;/** 小图. */private String productIcon;/** 状态, 0正常1下架. */private Integer productStatus;/** 类目编号. */private Integer categoryType;private Date createTime;private Date updateTime;public String getProductId() {return productId;}public void setProductId(String productId) {this.productId = productId;}public String getProductName() {return productName;}public void setProductName(String productName) {this.productName = productName;}public BigDecimal getProductPrice() {return productPrice;}public void setProductPrice(BigDecimal productPrice) {this.productPrice = productPrice;}public Integer getProductStock() {return productStock;}public void setProductStock(Integer productStock) {this.productStock = productStock;}public String getProductDescription() {return productDescription;}public void setProductDescription(String productDescription) {this.productDescription = productDescription;}public String getProductIcon() {return productIcon;}public void setProductIcon(String productIcon) {this.productIcon = productIcon;}public Integer getProductStatus() {return productStatus;}public void setProductStatus(Integer productStatus) {this.productStatus = productStatus;}public Integer getCategoryType() {return categoryType;}public void setCategoryType(Integer categoryType) {this.categoryType = categoryType;}public Date getCreateTime() {return createTime;}public void setCreateTime(Date createTime) {this.createTime = createTime;}public Date getUpdateTime() {return updateTime;}public void setUpdateTime(Date updateTime) {this.updateTime = updateTime;}
}

dao层ProductInfoRepository.java代码

package com.chengfeng.product.repository;import com.chengfeng.product.entity.ProductInfo;
import org.springframework.data.jpa.repository.JpaRepository;import java.util.List;public interface ProductInfoRepository extends JpaRepository<ProductInfo, String> {List<ProductInfo> findByProductStatus(Integer productStatus);
}

服务层ProductInfoServiceImpl.java代码

package com.chengfeng.product.service;import com.chengfeng.productmon.ProductStatusEnum;
import com.chengfeng.product.entity.ProductInfo;
import com.chengfeng.product.repository.ProductInfoRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;@Service
public class ProductInfoServiceImpl implements IProductInfoService {@Autowired(required = false)private ProductInfoRepository productInfoRepository;@Overridepublic List<ProductInfo> getProductList() {List<ProductInfo> productInfoList = productInfoRepository.findByProductStatus(ProductStatusEnum.UP.getCode());return productInfoList;}
}