SpringBoot 学习笔记2

使用数据库

SpringBoot使用JPA（Java Persistence API）资源库实现对数据库的操作。

JPA为POJO（Plain Ordinary Java Object）提供持久化的标准规范。将Java对象通过关系映射（ORM）持久化到数据库中。

在工程中引入JPA和MySQL的Maven依赖。

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

实体建模

部门实体，含有两个字段id和name。

其中的get和set方法可由idea自动生成。

@Table 指定关联数据库的表名

@Id 定义一条记录的唯一标识

@GeneratedValue 将其设置为自动生成。

package dbdemo.mysql.entity;

import javax.persistence.*;

@Entity
@Table(name = "department")
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    public Department() {
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

}

用户实体，含有三个字段id，name和createdate

@ManyToOne 定义与部门多对一关系，用did表示部门ID

@ManyToMany 定义与角色实体多对多关系，并用中间表user_role存储各自ID，表示对应关系

@DateTimeFormat 对日期数据格式化，保证在存取时正确

@JsonBackReference 防止关系对象递归访问

package dbdemo.mysql.entity;

import com.fasterxml.jackson.annotation.JsonBackReference;
import com.fasterxml.jackson.annotation.JsonIgnore;
import org.springframework.format.annotation.DateTimeFormat;

import javax.persistence.*;
import java.util.Date;
import java.util.List;

@Entity
@Table(name = "user")
public class User implements java.io.Serializable{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date createdate;

    @ManyToOne
    @JoinColumn(name = "did")
    @JsonBackReference
    private Department deparment;

    @ManyToMany(cascade = {}, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role",
            joinColumns = {@JoinColumn(name = "user_id")},
            inverseJoinColumns = {@JoinColumn(name = "roles_id")})
    private List<Role> roles;

    public User() {
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Date getCreatedate() {
        return createdate;
    }

    public void setCreatedate(Date createdate) {
        this.createdate = createdate;
    }

    public Department getDeparment() {
        return deparment;
    }

    public void setDeparment(Department deparment) {
        this.deparment = deparment;
    }

    public List<Role> getRoles() {
        return roles;
    }

    public void setRoles(List<Role> roles) {
        this.roles = roles;
    }
}

角色实体。含有id和name。

同样的，id唯一且自动生成

package dbdemo.mysql.entity;

import javax.persistence.*;

@Entity
@Table(name = "role")
public class Role implements java.io.Serializable{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    public Role() {
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

以上三个实体的定义实现了普通对象POJO与数据表的映射关系ORM

使用JPA持久化

UserRespository继承于JPA的JpaRepository接口

@Repository 将其定义为一个资源库，能被其他程序引用并提供存取数据库功能

注意使用的参数是各自的实体对象

package dbdemo.mysql.repository;

import dbdemo.mysql.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.Date;
import java.util.List;

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    User findByNameLike(String name);
    User readByName(String name);
    List<User> getByCreatedateLessThan(Date star);
}

JPA提供了自定义声明方法的规则，使用fingBy，getBy等作为前缀，与实体中的属性字段拼接，还可选拼接一些查询关键字即可组成一个查询方法。

这些方法不用实现，JPA会代理将其实现。

使用JPA的配置类

@EnableTransactionManagement 启用了JPA的事务管理

@EnableJpaRepositories 启用了JPA资源库并指定了上面接口资源库的位置

@EntityScan指定了定义实体的位置

package dbdemo.mysql.config;

import org.springframework.boot.orm.jpa.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;


@Order(Ordered.HIGHEST_PRECEDENCE)
@Configuration
@EnableTransactionManagement(proxyTargetClass = true)
@EnableJpaRepositories(basePackages = "dbdemo.**.repository")
@EntityScan(basePackages = "dbdemo.**.entity")
public class JpaConfiguration {

    @Bean
    PersistenceExceptionTranslationPostProcessor persistenceExceptionTranslationPostProcessor(){
        return new PersistenceExceptionTranslationPostProcessor();
    }

}

这个配置的参数是从配置文件中读取的，实际测试时的配置类把配置参数包含在类定义中

设置数据源和JPA的工作模式

创建数据库test，数据库的表结构会在运行时自动创建。同时授予本地测试用户root完全访问权限。

application.yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test?characterEncoding=utf8
    username: root
    password: 12345678
  jpa:
    database: MYSQL
    show-sql: true
  #Hibernate ddl auto (validate|create|create-drop|update)
    hibernate:
      ddl-auto: update
      naming-strategy: org.hibernate.cfg.ImprovedNamingStrategy
    properties:
      hibernate:
        dialect: org.hibernate.dialect.MySQL5Dialect

ddl-auto：update 表示使用Hibernate自动更新表结构，在数据表不存在时则创建，修改表结构时则在程序启动后同步更新。

MySQL测试实例

MysqlTest.java

package dbdemo.mysql.test;

import dbdemo.mysql.entity.Department;
import dbdemo.mysql.entity.Role;
import dbdemo.mysql.entity.User;
import dbdemo.mysql.repository.DepartmentRepository;
import dbdemo.mysql.repository.RoleRepository;
import dbdemo.mysql.repository.UserRepository;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.util.Assert;

import java.util.*;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {JpaConfiguration.class})
public class MysqlTest {
    private static Logger logger = LoggerFactory.getLogger(MysqlTest.class);

    @Autowired
    UserRepository userRepository;
    @Autowired
    DepartmentRepository departmentRepository;
    @Autowired
    RoleRepository roleRepository;

    @Before
    public void initData(){
        userRepository.deleteAll();
        roleRepository.deleteAll();
        departmentRepository.deleteAll();

        Department department = new Department();
        department.setName("开发部");
        departmentRepository.save(department);
        Assert.notNull(department.getId());

        Role role = new Role();
        role.setName("admin");
        roleRepository.save(role);
        Assert.notNull(role.getId());

        User user = new User();
        user.setName("user");
        user.setCreatedate(new Date());
        user.setDeparment(department);

        List<Role> roles = roleRepository.findAll();
        Assert.notNull(roles);
        user.setRoles(roles);

        userRepository.save(user);
        Assert.notNull(user.getId());
    }

    @Test
    public void findPage(){
        Pageable pageable = new PageRequest(0, 10, new Sort(Sort.Direction.ASC, "id"));
        Page<User> page = userRepository.findAll(pageable);
        Assert.notNull(page);
        for(User user : page.getContent()) {
            logger.info("====user==== user name:{}, department name:{}, role name:{}",
                    user.getName(), user.getDeparment().getName(), user.getRoles().get(0).getName());
        }
    }

    //@Test
    public void test(){
        User user1 = userRepository.findByNameLike("u%");
        Assert.notNull(user1);

        User user2 = userRepository.readByName("user");
        Assert.notNull(user2);

        List<User> users = userRepository.getByCreatedateLessThan(new Date());
        Assert.notNull(users);
    }
}

使用JUint测试，运行配置如下