在学习Springboot中 用到通用Mapper 调用其中的方法报NullPointerException
本帖最后由 冬马和纱 于 2019-8-27 00:57 编辑各位大哥帮我看看吧package pers.my.mapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import pers.my.pojo.User;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void test(){
System.out.println("1111111"+userMapper);
User user=userMapper.selectByPrimaryKey(1L);
System.out.println(user);
}
}package pers.my.mapper;
import pers.my.pojo.User;
import tk.mybatis.mapper.common.Mapper;
public interface UserMapper extends Mapper<User> {
}
package pers.my.pojo;
import lombok.Data;
import javax.persistence.Id;
import javax.persistence.Table;
@Data
@Table(name="t_user")
public class User {
@Id
private Integer id;
private String username;
private String password;
private String birthday;
private String gender;
}
package pers.my;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import tk.mybatis.spring.annotation.MapperScan;
@SpringBootApplication
@MapperScan("pers.my.mapper")
public class BootDemoApplication {
public static void main(String[] args) {
SpringApplication.run(BootDemoApplication.class);
}
}
<?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>pers.my.boot</groupId>
<artifactId>spring-boot</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.4.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.6</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<!--连接池用了通用mapper 不用自己配置了-->
<!--<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>-->
<!-- 驱动 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!--mybatis用了通用mapper 不用自己配置了-->
<!--<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.3.2</version>
</dependency>-->
<!--通用mapper-->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper-spring-boot-starter</artifactId>
<version>2.0.3</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
</dependency>
</dependencies>
</project>server:
servlet:
path: /
spring:
datasource:
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/edu
username: root
password: 123456
mybatis:
#configuration: 用了通用mapper 不用自己配置了
# map-underscore-to-camel-case: true
type-aliases-package: pers.my.pojo
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database.Cause: java.lang.NullPointerException
### The error may exist in pers/my/mapper/UserMapper.java (best guess)
### The error may involve pers.my.mapper.UserMapper.selectByPrimaryKey
### The error occurred while executing a query
### Cause: java.lang.NullPointerException
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
at com.sun.proxy.$Proxy71.selectOne(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:166)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:83)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
at com.sun.proxy.$Proxy83.selectByPrimaryKey(Unknown Source)
at pers.my.mapper.UserMapperTest.test(UserMapperTest.java:21)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
调用Mapper里面的方法 给我报NullPointerException 其他方法也是报这个 我把你的代码 复制了下来 跑了跑 没有问题...你对一下看看 我就数据库改了一下 因为字段不一样 你有mapper吗? namedlxd 发表于 2019-8-26 21:45
你有mapper吗?
啥意思我那个UserMapper继承了Mapper在之后打印userMapper也有对象 不是null 冬马和纱 发表于 2019-8-26 21:57
啥意思我那个UserMapper继承了Mapper在之后打印userMapper也有对象 不是null
放SQL的xml呢? namedlxd 发表于 2019-8-26 22:03
放SQL的xml呢?
用了这个通用mapper就不用xml了吧 冬马和纱 发表于 2019-8-26 22:15
用了这个通用mapper就不用xml了吧
你看下通用mapper的实现 冬马和纱 发表于 2019-8-26 22:15
用了这个通用mapper就不用xml了吧
我记得应该是要xml的，只是里面不写SQL，我也是萌新:lol namedlxd 发表于 2019-8-26 22:32
你看下通用mapper的实现
我看的这个视频 他说这些基本方法的sql它在底层帮你动态生成了我看他视频里面也确实没有配mapper.xml huang0817 发表于 2019-8-26 22:43
我记得应该是要xml的，只是里面不写SQL，我也是萌新
哈哈一起讨论 共同提升:lol
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