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

  1. 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>

  2. 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

  3. 根据DEPT表定义Dept实体类

     同上
     

  4. 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);
     
     }

  5. 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 {
     
     }

  6. 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());
         }
     }

  7. 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：

  1. 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?
     • ${}采用Statement执行机制，参数值拼到SQL中
     • SQL字段值位置使用#{}，字段名或表名位置使用${}

  2. 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

     1. 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>

     2. 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

     3. 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       
        
        }

     4. 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

     5. 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)

     6. 未完待续.........