工厂方法“dataSource”抛出 NullPointerException

Question

下面有关于这个问题的类似问题，但那里提供的解决方案对我没有帮助： Factory method 'dataSource' threw exception while startup 问题是我尝试使用 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，我收到了堆栈跟踪中显示的消息：

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

它检测到 DbConfig 类中的问题，该类抛出 NullPointerException。下面是 DbConfig.java 类：

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 pom.xml 依赖项和 application.properties 中的设置

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

主应用程序类如下所示：

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，请指出我在哪里做错了。 更新 我已经更改了 DbConfig 类 - 删除了 assert=false 并添加了 @Autowired private final Environment env ; 。 NullPointerException 消失但出现 BeanCreation 异常：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 行调用时

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

你会得到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;
    }
}

我还删除了assert false; 行，它有什么意义？它会抛出一个AssertionError 异常并破坏你的程序！

更新

对于错误：

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.

您必须更新您的 SQLite 驱动程序，您在 pom.xml 中使用的版本3.7.2 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

您不需要DbConfig。只需放下它并仅使用application.properties。 Spring Boot 会根据这些属性自动配置数据源。