IntelliJ IDEA 2017版 spring-boot使用Spring Data JPA使用Repository<T, T>编程

1、环境搭建pom.xml搭建

 <?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.spring</groupId>
     <artifactId>boot_jpa</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <packaging>jar</packaging>

     <name>boot_jpa</name>
     <url>http://maven.apache.org</url>
     <description>Demo project for Spring Boot</description>

     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
         <version>1.5.9.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-web</artifactId>
         </dependency>

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

         <!--自定义配置文件-->
         <dependency>
             <groupId>com.alibaba</groupId>
             <artifactId>fastjson</artifactId>
             <version>1.2.15</version>
         </dependency>

         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-jdbc</artifactId>
         </dependency>

         <!-- 添加fastjson 依赖包. -->
         <dependency>
             <groupId>com.alibaba</groupId>
             <artifactId>fastjson</artifactId>
             <version>1.2.15</version>
         </dependency>

         <!-- spring boot devtools 依赖包. -->
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-devtools</artifactId>
             <optional>true</optional>
             <scope>true</scope>
         </dependency>

         <!-- 添加MySQL数据库驱动依赖包. -->
         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
         </dependency>

         <!-- 添加Spring-data-jpa依赖. -->
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-data-jpa</artifactId>
         </dependency>

     </dependencies>

     <build>
         <plugins>
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
                 <configuration>
                     <!--fork :  如果没有该项配置，肯呢个devtools不会起作用，即应用不会restart -->
                     <fork>true</fork>
                 </configuration>
             </plugin>
         </plugins>
     </build>

 </project>

2、数据库连接搭建

 #######################################################
 ##datasource -- 指定mysql数据库连接信息.
 #######################################################
 spring.datasource.url = jdbc:mysql://localhost:3306/test
 spring.datasource.username = root
 spring.datasource.password = 123456
 spring.datasource.driverClassName = com.mysql.jdbc.Driver
 spring.datasource.max-active=20
 spring.datasource.max-idle=8
 spring.datasource.min-idle=8
 spring.datasource.initial-size=10

 ########################################################
 ### Java Persistence Api --  Spring jpa的配置信息.
 ########################################################
 # Specify the DBMS
 spring.jpa.database = MYSQL
 # Show or not log for each sql query
 spring.jpa.show-sql = true
 # Hibernate ddl auto (create, create-drop, update)
 spring.jpa.hibernate.ddl-auto = update
 # Naming strategy
 #[org.hibernate.cfg.ImprovedNamingStrategy  #org.hibernate.cfg.DefaultNamingStrategy]
 spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy
 # stripped before adding them to the entity manager)
 spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect

3、实体类建立

 package com.spring.boot.jap.perform.pojo;

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;

 /**
  * Created by liuya on 2018-01-26.
  */
 @Entity
 public class Cat {

     /**
      * 使用@Id指定主键.
      * <p>
      * 使用代码@GeneratedValue(strategy=GenerationType.AUTO)
      * 指定主键的生成策略，mysql默认的是自增长。
      */
     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
     private int id;//主键.

     private String catName;//姓名. cat_name

     private int catAge;//年龄. cat_age;

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public String getCatName() {
         return catName;
     }

     public void setCatName(String catName) {
         this.catName = catName;
     }

     public int getCatAge() {
         return catAge;
     }

     public void setCatAge(int catAge) {
         this.catAge = catAge;
     }

 }

4、dao层搭建（from位置会一直报错，但是不影响）

 package com.spring.boot.jap.perform.dao;

 import com.spring.boot.jap.perform.pojo.Cat;
 import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.query.Param;

 /**
  * Created by liuya on 2018-01-27.
  */
 public interface CatRepository extends Repository<Cat, Integer> {

     /**
      * 1/ 查询方法 以 get | find | read 开头.
      * 2/ 涉及查询条件时，条件的属性用条件关键字连接，要注意的是条件属性以首字母大写。
      */

     //根据catName进行查询 : 根据catName进行查询.
     //自定义方法访问方式一:
     public Cat findByCatName(String catName);

     //自定义方法访问方式二:
     /**
      * 如何编写JPQL语句，
      * 通过别名的方式查询用户
      */
     @Query("from Cat where catName=:Tommy")
     public Cat findMyCatOtherName(@Param("Tommy") String catName);

 }

5、service层搭建

 package com.spring.boot.jap.perform.service;

 import com.spring.boot.jap.perform.dao.CatRepository;
 import com.spring.boot.jap.perform.pojo.Cat;
 import org.springframework.stereotype.Service;

 import javax.annotation.Resource;
 import javax.transaction.Transactional;

 /**
  * Created by liuya on 2018-01-27.
  */

 @Service
 public class CatService {

     @Resource
     private CatRepository catRepository;

     //通过姓名查找用户信息
     public Cat findByCatName(String catName) {
         return catRepository.findByCatName(catName);
     }

     //通过JPQL语句别名查看用户信息
     public Cat findMyCatOtherName(String catName) {
         return catRepository.findMyCatOtherName(catName);
     }

 }

6、controller层搭建

 package com.spring.boot.jap.perform.controller;

 import com.spring.boot.jap.perform.pojo.Cat;
 import com.spring.boot.jap.perform.service.CatService;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;

 import javax.annotation.Resource;

 /**
  * Created by liuya on 2018-01-27.
  */

 @RestController
 @RequestMapping("/cat")
 public class CatController {

     @Resource
     private CatService catService;

     //通过姓名查找用户信息(用户的姓名不能重复要是唯一的)
     //访问连接:http://127.0.0.1:8080/cat/findByCatName?catName=jack
     @RequestMapping("/findByCatName")
     public Cat findByCatName(String catName) {
         return catService.findByCatName(catName);
     }

     //通过姓名查找用户信息(用户的姓名不能重复要是唯一的)方法三:
     //访问连接:http://127.0.0.1:8080/cat/findMyCatOtherName?catName=jack
     @RequestMapping("/findMyCatOtherName")
     public Cat findMyCatOtherName(String catName) {
         System.out.println("CatController.findMyCatOtherName()");
         return catService.findMyCatOtherName(catName);
     }

 }

7、Application层的搭建

 package com.spring.boot.jap.perform;

 import com.alibaba.fastjson.serializer.SerializerFeature;
 import com.alibaba.fastjson.support.config.FastJsonConfig;
 import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;

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

 @SpringBootApplication
 //@ComponentScan(basePackages = {"com.spring.boot.service.*"})
 public class BootJpaApplication {
     public static void main(String[] args) {
         SpringApplication.run(BootJpaApplication.class,args);
     }

     /**
      * 在这里我们使用 @Bean注入 fastJsonHttpMessageConvert
      *
      * @return
      */
     @Bean
     public HttpMessageConverters fastJsonHttpMessageConverters() {
         // 1、需要先定义一个 convert 转换消息的对象;
         FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();

         //2、添加fastJson 的配置信息，比如：是否要格式化返回的json数据;
         FastJsonConfig fastJsonConfig = new FastJsonConfig();
         fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat);

         //处理中文乱码
         List<MediaType> fastMediaTypes = new ArrayList<>();
         fastMediaTypes.add(MediaType.APPLICATION_JSON_UTF8);
         fastConverter.setSupportedMediaTypes(fastMediaTypes);

         //3、在convert中添加配置信息.
         fastConverter.setFastJsonConfig(fastJsonConfig);

         HttpMessageConverter<?> converter = fastConverter;
         return new HttpMessageConverters(converter);
     }
 }