springboot 整合 springdata

        用腻了ssm，尤其是mybatis，每次用户需求变动要求改表的时候都要删掉各种实体类和mapper.xml然后再重新生成，所以最近小研究了一下springdata，demo框架：springboot + springdata

        首先是maven的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.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.4.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>

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-devtools -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

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

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>


    </dependencies>

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


</project>

  springboot配置文件：application.properties

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/hrms?useUnicode=true&characterEncoding=utf8&useSSL=true
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.database=mysql
#自动建表
spring.jpa.hibernate.ddl-auto=update
#设置数据库方言
spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect
#打印sql
spring.jpa.show-sql=true

 spring.jpa.hibernate.ddl-auto配置自动建表，有四个属性

        create：每次启动时删除表，再根据实体类建表

        create-drop：每次启动时根据实体类建表，退出时删表

        update：每次启动时根据实体类更新表结构（表数据不变）

        validate：每次启动时根据实体类校验表结构

spring.jpa.database-platform配置数据库方言

        如果你的实体类中有外键，请配置此项，否则启动报错Specified key was too long; max key length is 1000 bytes，因为springdata默认的数据库方言是org.hibernate.dialect.MySQL5Dialect，数据库引擎是MyISAM，它既不支持高级事务也不支持外键。

以简单的系统管理为例，构建三个实体类UserEntity.java、RoleEntity.java、PermissionEntity.java：

UserEntity：

package com.example.demo.entity;

import javax.persistence.*;
import java.util.Objects;
import java.util.Set;

/**
 * @ClassName UserEntity
 * @Description TODO
 * @Author Rock-PC5
 * @Date 2018/9/19 13:45
 * @Version 1.0
 **/
@Entity
@Table(name = "user", schema = "hrms", catalog = "")
public class UserEntity {
	@Id
	@Column(name = "id")
	private String id;
	@Column(name = "username")
	private String username;
	@Column(name = "password")
	private String password;
	@ManyToMany
	@JoinTable(name = "user_role", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id")}, inverseJoinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id")})
	private Set<RoleEntity> roleEntitySet;

	public String getId() {
		return id;
	}

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

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public Set<RoleEntity> getRoleEntitySet() {
		return roleEntitySet;
	}

	public void setRoleEntitySet(Set<RoleEntity> roleEntitySet) {
		this.roleEntitySet = roleEntitySet;
	}
}

 RoleEntity：

package com.example.demo.entity;

import javax.persistence.*;
import java.util.Set;

/**
 * @ClassName RoleEntity
 * @Description TODO
 * @Author Rock-PC5
 * @Date 2018/9/19 13:45
 * @Version 1.0
 **/
@Entity
@Table(name = "role", schema = "hrms", catalog = "")
public class RoleEntity {
	@Id
	@Column(name = "id")
	private String id;
	@Column(name = "name")
	private String name;
	@Column(name = "description")
	private String description;
	@ManyToMany(mappedBy = "roleEntitySet")
	private Set<UserEntity> userEntitySet;
	@ManyToMany
	@JoinTable(name = "role_permission", joinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id")}, inverseJoinColumns = {@JoinColumn(name = "permission_id", referencedColumnName = "id")})
	private Set<PermissionEntity> permissionEntitySet;

	public String getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public Set<UserEntity> getUserEntitySet() {
		return userEntitySet;
	}

	public void setUserEntitySet(Set<UserEntity> userEntitySet) {
		this.userEntitySet = userEntitySet;
	}

	public Set<PermissionEntity> getPermissionEntitySet() {
		return permissionEntitySet;
	}

	public void setPermissionEntitySet(Set<PermissionEntity> permissionEntitySet) {
		this.permissionEntitySet = permissionEntitySet;
	}
}

PermissionEntity：

package com.example.demo.entity;

import javax.persistence.*;
import java.util.Objects;
import java.util.Set;

/**
 * @ClassName PermissionEntity
 * @Description TODO
 * @Author Rock-PC5
 * @Date 2018/9/19 13:45
 * @Version 1.0
 **/
@Entity
@Table(name = "permission", schema = "hrms", catalog = "")
public class PermissionEntity {
	@Id
	@Column(name = "id")
	private String id;
	@Column(name = "name")
	private String name;
	@Column(name = "description")
	private String description;
	@ManyToMany(mappedBy = "permissionEntitySet")
	private Set<RoleEntity> roleEntitySet;

	public String getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public Set<RoleEntity> getRoleEntitySet() {
		return roleEntitySet;
	}

	public void setRoleEntitySet(Set<RoleEntity> roleEntitySet) {
		this.roleEntitySet = roleEntitySet;
	}
}

简单介绍一下其中的注解：

@Entity：指明该类是一个实体类

@Table：指明该类与表的映射关系

        name指明该类所映射的表名，如果不写默认为类名

        schema指明该类所映射到的数据库，如果不写默认为连接到的数据库名

        catelog的作用与schema一致

@Id：指明该属性为主键

@Column：name指定该属性所对应的字段名

@ManyToMany：指明表间的多对多关系，mappedBy的作用是把维护表的任务交给与其关联的实体类，值为与其关联的实体类的对应外键的参数名。除此之外还有@ManyToOne，@OneToMany，@OneToOne等。

@JoinTable：新建第三张关联表来维护两实体类的关联关系

        name：新建表的表名

        joinColumns：该实体类对应表外键的字段名集合

        inverseJoinColumns：与其关联的实体类对应表外键的字段名集合

@JoinColumn：新建表中新建的字段

        name：新建的字段名

        referencedColumnName：该字段在主表中字段名

然后启动项目就可以了，生成的表如图所示：

在初体验springdata的时候，最直观的感受就是项目目录的简洁，完全不需要那些dao、service以及然人看了想吐的mapper.xml，仅仅需要一个jpa即可操作一个实体类：

那jpa的代码如下：

UserJpa：

package com.example.demo.jpa;

import com.example.demo.entity.UserEntity;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import java.io.Serializable;

/**
 * @ClassName UserJpa
 * @Description TODO
 * @Author Rock-PC5
 * @Date 2018/9/18 16:12
 * @Version 1.0
 **/
public interface UserJpa extends JpaRepository<UserEntity, String>, JpaSpecificationExecutor<UserEntity>, Serializable {

}

RoleJpa：

package com.example.demo.jpa;

import com.example.demo.entity.RoleEntity;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import java.io.Serializable;

/**
 * @ClassName RoleJpa
 * @Description TODO
 * @Author Rock-PC5
 * @Date 2018/9/19 13:16
 * @Version 1.0
 **/
public interface RoleJpa extends JpaRepository<RoleEntity, String>, JpaSpecificationExecutor<RoleEntity>, Serializable {
}

PermissionJpa：

package com.example.demo.jpa;

import com.example.demo.entity.PermissionEntity;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import java.io.Serializable;

/**
*@author FastKing
*@Description 
*@Date 15:03 2018/9/19
*@Param 
*@return 
**/
public interface PermissionJpa extends JpaRepository<PermissionEntity, String>, JpaSpecificationExecutor<PermissionEntity>, Serializable {

}

你只需要继承JpaRepository和JpaSpecificationExecutor，前者的第一个参数写对应实体类，第二个参数写对应实体类主键类型，后者的参数就是对应实体类

jpa的使用方法就和ssm中的service一样，这里给一个示例的Controller：

package com.example.demo.controller;

import com.example.demo.entity.UserEntity;
import com.example.demo.jpa.UserJpa;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Example;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @ClassName HelloController
 * @Description TODO
 * @Author FastKing
 * @Date 2018/9/13 9:02
 * @Version 1.0
 **/
@RestController
public class HelloController {

	@Autowired
	private UserJpa userJpa;

	@RequestMapping(value = "/login/{username}/{password}", method = RequestMethod.GET)
	public Object login(@PathVariable String username, @PathVariable String password) {
		UserEntity userEntity = new UserEntity();
		userEntity.setUsername(username);
		userEntity.setPassword(password);
		Example<UserEntity> userEntityExample = Example.of(userEntity);
		List<UserEntity> userList = userJpa.findAll(userEntityExample);
		return userList.size();
	}

	@RequestMapping(value = "/list")
	public Object list() {
		return userJpa.findAll();
	}
}

Example的用法可以类比Mybatis的xxxExample

---

更新一下三个实体类，

以UserEntity为例：

package com.example.demo.entity;

import javax.persistence.*;
import java.util.Set;

/**
 * @ClassName UserEntity
 * @Description TODO
 * @Author FastKing
 * @Date 2018/9/19 13:45
 * @Version 1.0
 **/
@Entity
@Table(name = "user", schema = "hrms", catalog = "")
public class UserEntity {
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "id" ,columnDefinition = ("int COMMENT 'id'"))
	private Integer id;
	@Column(name = "username" ,columnDefinition = ("varchar(255) COMMENT '用户名'"))
	private String username;
	@Column(name = "password" ,columnDefinition = ("varchar(255) COMMENT '密码'"))
	private String password;
	@Column(name = "salt",columnDefinition = ("varchar(255) COMMENT '盐值'"))
	private String salt;
	@Column(name = "isLocked",columnDefinition = ("tinyint COMMENT '是否锁定（0否1是）'"))
	private Byte isLocked;
	@Column(name = "isForbidden",columnDefinition = ("tinyint COMMENT '是否禁用（0否1是）'"))
	private Byte isForbidden;
	@ManyToMany
	@JoinTable(name = "user_role", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id",columnDefinition = ("int COMMENT '用户id'"))}, inverseJoinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id",columnDefinition = ("int COMMENT '角色id'"))})
	private Set<RoleEntity> roleEntitySet;

	public Integer getId() {
		return id;
	}

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

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public Set<RoleEntity> getRoleEntitySet() {
		return roleEntitySet;
	}

	public void setRoleEntitySet(Set<RoleEntity> roleEntitySet) {
		this.roleEntitySet = roleEntitySet;
	}

	public String getSalt() {
		return salt;
	}

	public void setSalt(String salt) {
		this.salt = salt;
	}

	public Byte getIsLocked() {
		return isLocked;
	}

	public void setIsLocked(Byte isLocked) {
		this.isLocked = isLocked;
	}

	public Byte getIsForbidden() {
		return isForbidden;
	}

	public void setIsForbidden(Byte isForbidden) {
		this.isForbidden = isForbidden;
	}
}

@Column中的columnDefinition用来定义对应数据库中的字段类型和注释，如果你要设置字段类型为varchar必须指定长度，否则报sql语法错误

@GeteratedValue如果设置为auto，mysql会自动选择squence自增策略，生成一个hibernate_squence表，用来记录其他表的主键。由于mysql不支持这种自增策略，改为identity即可