工厂方法'dataSource'抛出空指针异常

Question

下面有一个类似的问题，但提供的解决方案对我没有帮助:dataSource'启动时抛出异常问题是我试图用CRUD操作创建简单的Websocket应用程序。在成功构建后运行应用程序时，我得到的消息显示在堆栈跟踪中:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.springframework.cglib.core.ReflectUtils$1 (file:/home/admin1/.m2/repository/org/springframework/spring-core/5.0.8.RELEASE/spring-core-5.0.8.RELEASE.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of org.springframework.cglib.core.ReflectUtils$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2021-09-05 15:31:51.296 ERROR 14659 --- [ost-startStop-1] o.s.b.web.embedded.tomcat.TomcatStarter  : Error starting Tomcat context. Exception:
Constructor threw exception; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [com/example/websocket/configuration/DbConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [javax.sql.DataSource]: Factory method 'dataSource' threw exception; nested exception is java.lang.NullPointerException
Process finished with exit code 0

它检测DbConfig类内部的问题，抛出NullPointerException。下面是类DbConfig.java:

package com.example.websocket.configuration;
import lombok.RequiredArgsConstructor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import javax.sql.DataSource;
@RequiredArgsConstructor
@Configuration
public class DbConfig {
private final Environment env = null;
@Bean
public DataSource dataSource() {
final DriverManagerDataSource dataSource = new DriverManagerDataSource();
assert false;
dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name"));
dataSource.setUrl(env.getProperty("spring.datasource.url"));
dataSource.setUsername(env.getProperty("spring.datasource.username"));
dataSource.setPassword(env.getProperty("spring.datasource.password"));
return dataSource;
}
}

根据前面提到的问题，我还检查了application.properties

中的pom.xml依赖关系和设置。pom.xml

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>ch.simas.examples</groupId>
<artifactId>websocket</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.4.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
<version>2.0.4.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
<version>2.0.4.RELEASE</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<version>2.0.4.RELEASE</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.20</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
<version>2.0.4.RELEASE</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.7</version>
</dependency>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.25.0-GA</version>
</dependency>
<dependency>
<groupId>org.xerial</groupId>
<artifactId>sqlite-jdbc</artifactId>
<version>3.7.2</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

application.properties

server.port=8965
logging.level.root=INFO
spring.jpa.database-platform=com.example.websocket.configuration.SQLiteDialect
spring.jpa.hibernate.ddl-auto=create
spring.datasource.url=jdbc:sqlite:database.db
spring.datasource.driver-class-name=org.sqlite.JDBC
spring.datasource.username=**
spring.datasource.password=**
spring.jpa.show-sql=true

主应用程序类是这样的:

package com.example.websocket;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
@EnableWebSocket
@SpringBootApplication
public class WebsocketApp{
public static void main(String[] args) {
SpringApplication.run(WebsocketApp.class, args);
}
}

如果可能的话，请指出我做错的地方。更新我已经改变了DbConfig类-删除assert=false并添加@Autowired private final Environment env ;。NullPointerException消失了，但是出现了一个BeanCreation Exception:org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]:Receiver class org.sqlite.Conn does not define or inherit an implementation of the resolved method 'abstract boolean isValid(int)' of interface java.sql.Connection.

Answer 1

您的env对象是null:

private final Environment env = null;

所以在第21行调用

env.getProperty("spring.datasource.driver-class-name")

你得到了NullPointerException。

您应该在DbConfig类中注入(@Autowired)Environment(并删除final修饰符):

@RequiredArgsConstructor
@Configuration
public class DbConfig {
@Autowired
private Environment env;
@Bean
public DataSource dataSource() {
final DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name"));
dataSource.setUrl(env.getProperty("spring.datasource.url"));
dataSource.setUsername(env.getProperty("spring.datasource.username"));
dataSource.setPassword(env.getProperty("spring.datasource.password"));
return dataSource;
}
}

我也删除了assert false;行，它的意义是什么?它将抛出一个AssertionError异常并破坏你的程序!

错误:

Receiver class org.sqlite.Conn does not define or inherit an implementation of the resolved method 'abstract boolean isValid(int)' of interface java.sql.Connection.

你必须更新你的SQLite驱动程序，版本3.7.2你正在使用的pom.xml是ancient！ 它可以追溯到2010年!

<dependency>
<groupId>org.xerial</groupId>
<artifactId>sqlite-jdbc</artifactId>
<version>3.7.2</version>
</dependency>

使用最新版本，例如

<version>3.36.0.3</version>

Answer 2

不需要DbConfig。只需删除它并仅使用application.properties。Spring Boot将根据这些属性自动配置数据源。