Spring Boot配置QueryDSL（生成Query查询实体类，查询数据）

快来打我* 2022-09-11 06:20 365阅读 0赞

## 1 QueryDSL ##

QueryDSL仅仅是一个通用的查询框架，专注于通过Java API构建类型安全的SQL查询。

Querydsl可以通过一组通用的查询API为用户构建出适合不同类型ORM框架或者是SQL的查询语句，也就是说QueryDSL是基于各种ORM框架以及SQL之上的一个通用的查询框架。

借助QueryDSL可以在任何支持的ORM框架或者SQL平台上以一种通用的API方式来构建查询。目前QueryDSL支持的平台包括JPA，JDO，SQL，Java Collections，RDF，Lucene，Hibernate Search。

## 2 Maven依赖 ##

<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-data-jpa</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    			<scope>runtime</scope>
    		</dependency>
    		<dependency>
    			<groupId>org.projectlombok</groupId>
    			<artifactId>lombok</artifactId>
    			<optional>true</optional>
    		</dependency>
    		
    		<dependency>
    			<groupId>cn.hutool</groupId>
    			<artifactId>hutool-all</artifactId>
    			<version>5.5.1</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>com.querydsl</groupId>
    			<artifactId>querydsl-jpa</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>com.querydsl</groupId>
    			<artifactId>querydsl-apt</artifactId>
    			<scope>provided</scope>
    		</dependency>

## 3 Maven插件 ##

<plugin>
                    <groupId>com.mysema.maven</groupId>
                    <artifactId>apt-maven-plugin</artifactId>
                    <version>1.1.3</version>
                    <executions>
                        <execution>
                            <goals>
                                <goal>process</goal>
                            </goals>
                            <configuration>
                                <outputDirectory>target/generated-sources/java</outputDirectory>
                                <processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>
                            </configuration>
                        </execution>
                    </executions>
                </plugin>

## 4 Spring Boot配置 ##

#连接mysql数据库
    spring.datasource.url = jdbc:mysql://localhost:3306/xudongbase?useUnicode=true&characterEncoding=utf8&useOldAliasMetadataBehavior=true&useTimezone=true&serverTimezone=GMT%2B8&useLegacyDatetimeCode=false
    spring.datasource.username = root
    spring.datasource.password = xudong123456
    spring.jpa.database = mysql

## 5 UserEntity ##

用户信息实体类。

package com.entity;
     
    import lombok.Data;
     
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.Table;
     
    /**
     * 用户信息实体类
     */
    @Data
    @Table(name = "users")
    @Entity
    public class UserEntity {
        /**
         * 用户名
         */
        @Column(name = "username")
        @Id
        private String username;
        /**
         * 昵称
         */
        @Column(name = "pickname")
        private String pickname;
        /**
         * 密码
         */
        @Column(name = "password")
        private String password;
        /**
         * 性别
         */
        @Column(name = "sex")
        private String sex;
    }

## 6 生成Query查询实体类 ##

### 6.1 配置项目的maven命令 ###

第一步，点击Run->Edit Configurations，进入Run/Debug Configurations窗口。

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第二步， 点击+号，再点击Maven，生成一条Maven配置。

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第三步，在Comand line 输入 compile，点击Apply。

### ![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5pet5Lic5oCq_size_20_color_FFFFFF_t_70_g_se_x_16 2][]6.2 生成Query查询实体类 ###

第一步，点击运行按钮，生成Query查询实体类。

![watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA5pet5Lic5oCq_size_20_color_FFFFFF_t_70_g_se_x_16 3][]

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## 7 UserRepository ##

package com.dao;
    
    import com.entity.UserEntity;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.querydsl.QuerydslPredicateExecutor;
    
    public interface UserRepository extends JpaRepository<UserEntity,Long>, QuerydslPredicateExecutor<UserEntity> {
    }

## 8 调试代码 ##

package com.controller;
    
    import com.dao.UserRepository;
    import com.entity.QUserEntity;
    import com.entity.UserEntity;
    import com.querydsl.core.types.dsl.BooleanExpression;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    import java.util.stream.Collectors;
    import java.util.stream.StreamSupport;
    
    @RestController
    public class UserController {
        @Autowired
        private UserRepository userRepository;
    
        /**
         * 获取用户信息
         *
         * @param username 用户名
         * @return
         */
        @GetMapping("/getUserList")
        public List<UserEntity> getUserList(@RequestParam String username) {
            //查询实体
            QUserEntity qUserEntity = QUserEntity.userEntity;
            BooleanExpression expression = qUserEntity.username.contains(username);
            List<UserEntity> userEntityList = StreamSupport.stream(userRepository.findAll(expression).spliterator(),false).collect(Collectors.toList());
            return userEntityList;
        }
    }

## 9 调试结果 ##

### 9.1 查询数据 ###

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