Spring Boot+JPA+Mysql+ThymeLeaf快速构建CURD系统（三）构建后端

上一篇我们已经成功搭建了一个SpringBoot的工程，在这个基础上实现一个通信录功能的CURD的Demo程序，本篇讲述如何构建后端部分。

由于重点是演示SpringBoot，我们就简化这个通信录，在Mysql中新建一个Person表，包含Id，Name和Phone三个字段，初始化SQL语句如下：

CREATE TABLE `Person` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(11) DEFAULT NULL,
  `phone` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

为了在SpringBoot中连接Mysql数据库，首先在pom文件中增加如下三个依赖：

        <dependency>
            <groupId>org.springframework.datagroupId>
            <artifactId>spring-data-jpaartifactId>
        dependency>
        <dependency>
            <groupId>org.hibernategroupId>
            <artifactId>hibernate-entitymanagerartifactId>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
        dependency>

增加后进行Maven Update Project后在Maven Dependency中就可以看到新增的依赖包。

新建一个package，名字为jpa，用来放数据库相关的处理的类，新建一个类DataSourceConfig.java，代码如下：

package com.springBoot.curdDemo.jpa;

import java.util.Properties;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@Configuration
@EnableTransactionManagement
public class DataSourceConfig {

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://***.***.***.***:3306/curdDemo?useUnicode=true&characterEncoding=UTF-8");// 填入你的mysql的访问url
        dataSource.setUsername("***");// mysql用户名
        dataSource.setPassword("***");// mysql访问密码
        return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean entityManagerFactory = new LocalContainerEntityManagerFactoryBean();

        entityManagerFactory.setDataSource(dataSource);

        entityManagerFactory.setPackagesToScan("com.springBoot.curdDemo.jpa.entity");// mapping类的存放路径

        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        entityManagerFactory.setJpaVendorAdapter(vendorAdapter);

        Properties additionalProperties = new Properties();
        additionalProperties.put("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
        additionalProperties.put("hibernate.show_sql", "false");
        additionalProperties.put("hibernate.hbm2ddl.auto", "none");
        entityManagerFactory.setJpaProperties(additionalProperties);

        return entityManagerFactory;
    }

    @Bean
    public JpaTransactionManager transactionManager() {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(
                entityManagerFactory.getObject());
        return transactionManager;
    }

    @Bean
    public PersistenceExceptionTranslationPostProcessor exceptionTranslation() {
        return new PersistenceExceptionTranslationPostProcessor();
    }

    @Autowired
    private DataSource dataSource;

    @Autowired
    private LocalContainerEntityManagerFactoryBean entityManagerFactory;
}

这个类用于配置和MySql的连接以及Hibernate的属性，Spring 3以后的中心思想就是”约定大于配置”，这里配置了DataSource, LocalContainerEntityManagerFactoryBean, JpaTransactionManager等Bean在Spring的上下文中，由于我们只配置了这些数据库相关的Bean，Spring会自动使用这些Bean作为JPA的底层配置。

我们配置了mapping类的存放路径为com.springBoot.curdDemo.jpa.entity，那么下一步就新建这个package，然后建立一个类来mapping数据库中的Person表。该类代码如下：

package com.springBoot.curdDemo.jpa.entity;

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

@Entity
@Table(name = "Person")
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Integer id;

    @Column(name = "name")
    private String name;

    @Column(name = "phone")
    private String phone;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

}

数据库部分最后构建一个Respository接口，代码如下：

package com.springBoot.curdDemo.jpa;

import org.springframework.data.repository.PagingAndSortingRepository;

import com.springBoot.curdDemo.jpa.entity.Person;

public interface PersonRespository extends PagingAndSortingRepository<Person, Integer> {

}

数据库部分构建完毕后，构建Service层，本文的Service层就直接写4个方法，对应CURD，源码如下：

package com.springBoot.curdDemo.service;

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

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.springBoot.curdDemo.jpa.PersonRespository;
import com.springBoot.curdDemo.jpa.entity.Person;

@Service
public class PersonService {

    @Autowired
    PersonRespository personRespository;

    public void create(String name, String phone) {
        Person person = new Person();
        person.setName(name);
        person.setPhone(phone);
        personRespository.save(person);
    }

    public void update(Integer id, String name, String phone) {
        Person person = personRespository.findOne(id);
        person.setName(name);
        person.setPhone(phone);
        personRespository.save(person);
    }

    public List read() {
        List persons = new ArrayList();
        Iterator it = personRespository.findAll().iterator();
        while (it.hasNext()) {
            Person person = it.next();
            persons.add(person);
        }
        return persons;
    }

    public void delete(Integer id) {
        personRespository.delete(id);
    }
}

至此，后端部分就构建完毕了，这是目录结构如下：