我尝试在 Spring Boot 中将 Query DSL 与 MongoDB 结合使用，但出现错误。该应用程序在不使用 MongoDB 查询 DSL 库的情况下成功运行。我想使用这个库，因为我想使用更复杂的查询。代码应该可以工作，我认为某处有一点错误。

问题是当我点击 Maven 包时出现这些错误，不幸的是我无法在此处发布所有输出:

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'hotelController' defined in file [C:\Users\dgs\IdeaProjects\springboot-mongodb\target\classes\com\dgs\springbootmongodb\controller\HotelController.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'hotelController' defined in file [C:\Users\dgs\IdeaProjects\springboot-mongodb\target\classes\com\dgs\springbootmongodb\controller\HotelController.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!

[ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 4.26 s <<< FAILURE! - in com.dgs.springbootmongodb.SpringbootMongodbApplicationTests
[ERROR] contextLoads(com.dgs.springbootmongodb.SpringbootMongodbApplicationTests)  Time elapsed: 0.001 s  <<< ERROR!
java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'hotelController' defined in file [C:\Users\dgs\IdeaProjects\springboot-mongodb\target\classes\com\dgs\springbootmongodb\controller\HotelController.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hotelRepository': Invocation of init method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.repository.support.QuerydslMongoPredicateExecutor]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!
Caused by: java.lang.IllegalArgumentException: Did not find a query class com.dgs.springbootmongodb.models.QHotel for domain class com.dgs.springbootmongodb.models.Hotel!
Caused by: java.lang.ClassNotFoundException: com.dgs.springbootmongodb.models.QHotel

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.21.0:test (default-test) on project springboot-mongodb: There are test failures.

这是一个酒店预订应用程序，这是代码:

酒店模型:

package com.dgs.springbootmongodb.models;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.index.IndexDirection;
import org.springframework.data.mongodb.core.index.Indexed;
import org.springframework.data.mongodb.core.mapping.Document;

import java.util.ArrayList;
import java.util.List;

// The Hotel is the aggregate root so this is the entity on which we will apply our annotations

    @Document(collection = "Hotels")
    public class Hotel {

        @Id
        private String id;
        private String name;

        @Indexed(direction = IndexDirection.ASCENDING)
        private int pricePerNight;
        private Address address;
        private List<Review> reviews;

        protected Hotel() {
            this.reviews = new ArrayList<>();
        }

        public Hotel(String name, int pricePerNight, Address address, List<Review> reviews) {
            this.name = name;
            this.pricePerNight = pricePerNight;
            this.address = address;
            this.reviews = reviews;
        }

        public String getId() {
            return id;
        }

        public String getName() {
            return name;
        }

        public int getPricePerNight() {
            return pricePerNight;
        }

        public Address getAddress() {
            return address;
        }

        public List<Review> getReviews() {
            return reviews;
        }
    }

HotelRepository 接口(interface):

package com.dgs.springbootmongodb.dao;

import com.dgs.springbootmongodb.models.Hotel;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.data.mongodb.repository.Query;
import org.springframework.data.querydsl.QuerydslPredicateExecutor;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface HotelRepository extends MongoRepository<Hotel, String>, QuerydslPredicateExecutor<Hotel> {

    // findBy + PricePerNight (property name) + LessThan (filter)

    List<Hotel> findByPricePerNightLessThan(int maxPrice);

    @Query(value = "{address.city:?0}")
    List<Hotel> findByCity(String city);
}

酒店 Controller :

package com.dgs.springbootmongodb.controller;

import com.dgs.springbootmongodb.dao.HotelRepository;
import com.dgs.springbootmongodb.models.Hotel;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Optional;

@RestController
@RequestMapping("/hotels")
public class HotelController {

    private HotelRepository hotelRepository;

    public HotelController(HotelRepository hotelRepository) {
        this.hotelRepository = hotelRepository;
    }

    @GetMapping("/all")
    public List<Hotel> getAllHotels() {

        List<Hotel> hotels = hotelRepository.findAll();

        return hotels;
    }

    @GetMapping("/{id}")
    public Optional<Hotel> getOneHotel(@PathVariable String id) {

        return hotelRepository.findById(id);
    }

    @PostMapping
    public Hotel create(@RequestBody Hotel hotel) {

        return hotelRepository.save(hotel);
    }

    @PutMapping
    public Hotel update(@RequestBody Hotel hotel) {

        return hotelRepository.save(hotel);
    }

    @DeleteMapping("/delete/{id}")
    public List<Hotel> delete(@PathVariable String id) {

        hotelRepository.deleteById(id);

        return hotelRepository.findAll();
    }

    @GetMapping("/price/{maxPrice}")
    public List<Hotel> getByPricePerNight(@PathVariable int maxPrice) {

        List<Hotel> hotels = hotelRepository.findByPricePerNightLessThan(maxPrice);

        return hotels;
    }

    @GetMapping("address/{city}")
    public List<Hotel> getByCity(@PathVariable String city) {

        List<Hotel> hotels = hotelRepository.findByCity(city);

        return hotels;
    }
}

这是 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>com.dgs</groupId>
    <artifactId>springboot-mongodb</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springboot-mongodb</name>
    <description>Demo project for Spring Boot with Mongo DB</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.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-data-mongodb</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-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- Add support for Mongo Query DSL -->

        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-mongodb</artifactId>
            <version>4.1.3</version>
            <exclusions>
                <exclusion>
                    <groupId>org.mongodb</groupId>
                    <artifactId>mongo-java-driver</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

    </dependencies>

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

            <!-- Add plugin for Mongo Query DSL -->

            <plugin>
                <groupId>com.mysema.maven</groupId>
                <artifactId>apt-maven-plugin</artifactId>
                <version>1.1.3</version>
                <dependencies>
                    <dependency>
                        <groupId>com.querydsl</groupId>
                        <artifactId>querydsl-apt</artifactId>
                        <version>4.1.3</version>
                    </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>process</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>target/generated-sources/annotations</outputDirectory>
                            <processor>
                                org.springframework.data.mongodb.repository.support.MongoAnnotationProcessor
                            </processor>
                            <logOnlyOnError>true</logOnlyOnError>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>


</project>

更新

这是入门级:

@SpringBootApplication
public class SpringbootMongodbApplication {

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

这是应用程序的结构:

最佳答案

删除目标文件夹并重新开始。

apt-maven-plugin 生成、编译源代码并添加到类路径中。将插件的输出目录调整为 target/generated-sources/apt。

运行 maven 包阶段并验证 Q 类文件在目标/类位置的模型包内，Q 源文件在 target/generated-sources/apt 的模型包内。

关于java - 如何在 Spring Boot 中使用查询 DSL 和 MongoDB，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52344964/