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;
@Override
public 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=product
server.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 = 123456
spring.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="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.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>https://repo.spring.io/milestone</url>
</repository>
</repositories>
</project>
application.properties代码：
spring.application.name=product
server.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 = 123456
spring.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 {
@Autowired
private 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 {
@Id
private 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.product.common.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;
@Override
public List<ProductInfo> getProductList() {
List<ProductInfo> productInfoList = productInfoRepository.findByProductStatus(ProductStatusEnum.UP.getCode());
return productInfoList;
}
}
