按示例进行Spring数据查询

Question

我有对象FilterData。

@Entity
@Getter
@Setter
@ToString
@NoArgsConstructor(access = AccessLevel.PUBLIC)
public class FilterData implements Serializable {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private long id;

    @Size(max = 20)
    private String imsi;

    @Size(max = 10)
    private String mcc;

    @Size(max = 10)
    private String mnc;

    public FilterData(String imsi, String mcc, String mnc){
        this.imsi = imsi;
        this.mcc = mcc;
        this.mnc = mnc;
    }
}

库：

@RepositoryRestResource
public interface FilterDataRepository extends JpaRepository<FilterData, Long> {}

依赖关系：

<?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>com.example</groupId>
    <artifactId>my-project</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>

    <name>Project Demo</name>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <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>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

测试：

package com.example;

import com.example.orm.FilterData;
import com.example.repository.FilterDataRepository;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.ExampleMatcher;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@EnableJpaRepositories
@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Bean
    public CommandLineRunner demo(FilterDataRepository filterDataRepository){
        return (args) -> {

            FilterData fd1 = new FilterData("12345", "219", "01");
            FilterData fd2 = new FilterData("12345", "219", "02");
            FilterData fd3 = new FilterData("56789", "218", "10");
            FilterData fd4 = new FilterData("56789", "222", "02");
            FilterData fd5 = new FilterData("10010", "443", "44");

            filterDataRepository.save(fd1);
            filterDataRepository.save(fd2);
            filterDataRepository.save(fd3);
            filterDataRepository.save(fd4);
            filterDataRepository.save(fd5);


            FilterData fd = new FilterData();
            fd.setMcc("218");

            ExampleMatcher matcher = ExampleMatcher.matching()
                    .withIncludeNullValues();

            Example<FilterData> ex = Example.of(fd, matcher);
            System.out.println(filterDataRepository.findAll()); // prints all

            System.out.println(filterDataRepository.count(ex)); // 0
            System.out.println(filterDataRepository.findOne(ex)); // null
            System.out.println(filterDataRepository.findAll(ex)); // [] empty
        };
    }
}

当我尝试“findAll（）”时，我得到了所有对象，但是当我尝试从示例中查询时，我无法得到任何东西。

当我尝试时，我通过示例跟随spring数据jpa查询

有什么建议吗？

Answer 1

将匹配器更新为：

ExampleMatcher matcher = ExampleMatcher.matching().withIncludeNullValues().withIgnorePaths("id","imsi", "mnc");

你没有得到任何东西，因为matcher正在查询所有的字段匹配但是你只对mcc感兴趣，你需要告诉忽略其他字段。

Answer 2

问题是由于存储库正在查找JPA实体ID，在这种情况下，它正在寻找ID = 0.此外，未设置的值为null，需要在匹配器中忽略。

您只需要忽略标识字段

ExampleMatcher.matching().withIgnoreNullValues()
    .withIgnorePaths("id");