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SpringBoot数据库访问(一)--------关系型数据库访问（RDBMS）

关系型数据库访问（RDBMS）

采用JdbcTemplate、MyBatis、JPA、Hibernate等技术。

一、JdbcTemplate工具

在pom.xml添加boot-starter-jdbc定义

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.7.RELEASE</version>
    </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><!-- jdbc -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        
        <dependency>
        <groupId>com.oracle</groupId><!-- oracle的版本-->
        <artifactId>ojdbc6</artifactId>
        <version>11.2.0.3</version>
        </dependency>
    </dependencies>

在application.properties添加链接参数定义

spring.datasource.username=SCOTT
spring.datasource.password=TIGER
spring.datasource.url=jdbc:oracle:thin:@localhost:1521:XE
spring.datasource.driverClassName=oracle.jdbc.OracleDriver

根据DEPT表编写Dept实体类

public class Dept implements Serializable{

    private Integer deptno;
    private String dname;
    private String loc;

    //set和get省略
}

定义DeptDao接口

public interface DeptDao {

    public List<Dept> findAll();

}

定义JdbcDeptDao实现类

@Repository("deptDao")
public class JdbcDeptDao implements DeptDao {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    public List<Dept> findAll() {
        String sql = "select * from DEPT";
        //BeanPropertyRowMapper功能同名加载。查询结果集列名和实体类属性名一致,类似写了一个Maper
        RowMapper<Dept> rowMapper = new BeanPropertyRowMapper<Dept>(Dept.class);
        List<Dept> list = jdbcTemplate.query(sql, rowMapper);
        return list;
    }

}

定义主启动类，开启自动配置和扫描等功能

@SpringBootApplication
public class MyBootApplication {

}

测试程序

public static void main(String[] args) {
    ApplicationContext ac =  SpringApplication.run(MyBootApplication.class);
    DeptDao deptDao = ac.getBean("deptDao",DeptDao.class);
    List<Dept> list = deptDao.findAll();
    for(Dept dept:list){
        System.out.println(dept.getDeptno()
            +" "+dept.getDname()+" "+dept.getLoc());
    }
}

二、MyBatis工具

在pom.xml添加boot-starter-jdbc、mybatis-boot定义

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.7.RELEASE</version>
</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-jdbc</artifactId>
    </dependency>

    <dependency>
        <groupId>com.oracle</groupId>
        <artifactId>ojdbc6</artifactId>
        <version>11.2.0.3</version>
    </dependency>

    <!-- mybatis、mybatis-spring、autocofigurer -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.3.0</version>
    </dependency>

</dependencies>

在application.properties添加数据库连接参数定义

spring.datasource.username=SCOTT
spring.datasource.password=TIGER
spring.datasource.url=jdbc:oracle:thin:@localhost:1521:XE
spring.datasource.driverClassName=oracle.jdbc.OracleDriver

根据DEPT表定义Dept实体类
```
同上
```

定义Mapper映射器DeptDao接口、利用注解定义SQL

public interface DeptDao {

    @Select("select * from DEPT") 
    public List<Dept> selectAll();

    @Select("select * form DEPT where DEPTNO=#{no}")
    public Dept selectById(int id);

    @Insert("insert into DEPT(DEPTNO,DNAME,LOC) values (#{deptno},#{dname},#{loc})")
    public void save(Dept dept);

}

定义主启动类，添加MapperScan标记

@SpringBootApplication
@MapperScan(basePackages={"cn.xdl.dao"}) //扫描指定包中的dao类
public class MyBootApplication {

}

测试程序

public static void main(String[] args) {
    ApplicationContext ac =  SpringApplication.run(MyBootApplication.class, args);
    DeptDao deptDao = ac.getBean("deptDao",DeptDao.class);
    List<Dept> list = deptDao.selectAll();
    for(Dept dept:list){
        System.out.println(dept.getDeptno()+" "+dept.getDname());
    }
}

追加pageHelper分页处理

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.2.3</version>
</dependency> <!-- 指定添加一个分页组件pageHelp-->

然后在调用查询方法前，执行下PageHelper.startPage()方法即可

PageHelper.startPage(2, 3);
List<Dept> list = deptDao.selectAll();

Mybatis使用注意问题：

SQL参数使用#{}和${}的区别
- 采用#{}格式，预编译SQL执行机制，SQL发送时采用?
- ${}采用Statement执行机制，参数值拼到SQL中
- SQL字段值位置使用#{}，字段名或表名位置使用${}

异常："无效列类型:1111"

参数#{}遇到null值情况，会提示上述异常。在可能为null参数位置，使用#{}时，需要指定jdbcType属性，例如#{xx,jdbcType=XXX}

三、JPA工具

在pom.xml追加boot-jdbc、boot-data-jpa包定义

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.1.RELEASE</version>
</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-jdbc</artifactId>
    </dependency>

    <dependency>
        <groupId>com.oracle</groupId>
        <artifactId>ojdbc6</artifactId>
        <version>11.2.0.3</version>
    </dependency>

    <!-- jpa -->
    <dependency>
        <groupId>org.springframework.boot</groupId><!-- 导入jpa的jar包 -->
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

</dependencies>

在application.properties文件追加数据库连接参数定义

spring.datasource.username=SCOTT
spring.datasource.password=TIGER
spring.datasource.url=jdbc:oracle:thin:@localhost:1521:XE
spring.datasource.driverClassName=oracle.jdbc.OracleDriver

根据DEPT表编写Dept实体类，并追加映射注解标记

@Entity  //标识为实体类
@Table(name="DEPT")  //标识为数据库中的表名
public class Dept implements Serializable{

    @Id  //指定前的字段为主键
    @Column(name="DEPTNO") //指定目标字段与当前字段相同
    private Integer deptno;

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

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

    //省略set和get方法       

}

定义DeptDao接口，可以继承JpaRepository
```
public interface DeptDao extends JpaRepository<Dept, Integer>{

}
```
Repository：顶级接口，无任何操作

CrudRepository：继承了Repository，增加了增删改查操作方法

PagingAndSortingRepository：继承CrudRepository，增加了分页和排序操作

JpaRepository：继承了PagingAndSortingRepository，增加批处理操作

测试程序

public static void main(String[] args) {
    ApplicationContext ac = 
        SpringApplication.run(MyBootApplication.class, args);
    DeptDao deptDao = ac.getBean("deptDao",DeptDao.class);
    List<Dept> list = deptDao.findAll();
    for(Dept dept:list){
        System.out.println(dept.getDeptno()+" "+dept.getDname());
    }
}
Sql语句中常用连接词

四、Hibernate工具(后续讲解)

```
未完待续.........
```

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原文地址：https://www.cnblogs.com/hx1098/p/9398630.html