介绍三种操作数据库的对比
第一种直接JDBC
思路：写个工具类，获取连接的方法，释放资源的方法
-
实现：
pom.xml添加mysql驱动包mysql mysql-connector-java 5.1.38 junit junit 4.10 写工具类utils.java
public class JdbcUtils { public static Connection getConn() throws Exception{} public static void release(ResultSet rs, Statement sm, Connection conn){} }写单元测试test.java
public class JDBCUtilsTest { @Test public void testGetConn() throws Exception { Connection connection = JDBCUtils.getConnection(); Assert.assertNotNull(connection); } }
写业务代码
先实体entity/Student.java
public class Student {
private int id;
private String name;
private int age;
get()/set()...
}
在数据接口层dao/StudentDao.java
public interface StudentDao {
public List queryAllStudent();
public void saveStudent(Student student);
}
在数据实现层dao/StudentDaoImpl.java
public class StudentDaoImpl implements StudentDao{
@Override
public List queryAllStudent() {
List list = new ArrayList<>();
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
connection = JDBCUtils.getConnection();
String sql = "select * from student";
statement = connection.prepareStatement(sql);
resultSet = statement.executeQuery();
while (resultSet.next()) {
Student student = new Student();
student.setId(resultSet.getInt("id"));
student.setName(resultSet.getString("name"));
student.setAge(resultSet.getInt("age"));
list.add(student);
}
}catch (Exception e){
e.printStackTrace();
}finally {
JDBCUtils.release(resultSet,statement,connection);
}
return list;
}
@Override
public void saveStudent(Student student) {
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
try {
connection = JDBCUtils.getConnection();
String sql = "insert into student (name,age) values (?,?)";
statement = connection.prepareStatement(sql);
statement.setString(1,student.getName());
statement.setInt(2,student.getAge());
statement.executeUpdate();
}catch (Exception e){
e.printStackTrace();
}finally {
JDBCUtils.release(resultSet,statement,connection);
}
}
}
第二种就是spring Template
痛点：在第一种写业务代码时，与数据库交互都需要处理
Connection,Statement,ResultSet对象，很繁琐思路：通过操作模板就能执行sql语句操作数据库
通过bean来维护所有人，datasource，template，dao层
在bean里面把datasource引入template，在数据实现层引入template，在实现层的代码中get/set注入属性，通过属性操作db
这种思路的好处，重复代码只需要通过bean管理dao，在dao注入属性，即可操作数据库-
实现：
pom.xml添加jar包org.springframework spring-jdbc 4.3.5.RELEASE org.springframework spring-context 4.3.5.RELEASE
写resources/beans.xml配置
写单元测试test.java
public class DataSourceTest {
private ApplicationContext context = null;
@Before
public void createContext(){
context = new ClassPathXmlApplicationContext("beans.xml");
}
@After
public void distoryContext(){
context = null;
}
@Test
public void testDataSource(){
DataSource dataSource = (DataSource) context.getBean("dataSource");
Assert.assertNotNull(dataSource);
}
写业务代码
先实体entity/Student.java
public class Student {
private int id;
private String name;
private int age;
get()/set()...
}
在数据接口层dao/StudentDao.java
public interface StudentDao {
public List queryAllStudent();
public void saveStudent(Student student);
}
在数据实现层dao/StudentDaoImpl.java
public class SpringJdbcImpl implements StudentDao {
//在数据实现层代码中set/get注入模板属性
private JdbcTemplate jdbcTemplate;
public JdbcTemplate getJdbcTemplate() {
return jdbcTemplate;
}
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
@Override
public List queryAllStudent() {
final List list = new ArrayList<>();
String sql = "select * from student";
jdbcTemplate.query(sql,new RowCallbackHandler(){
@Override
public void processRow(ResultSet rs) throws SQLException {
Student student = new Student();
student.setId(rs.getInt("id"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));
list.add(student);
}
});
return list;
}
@Override
public void saveStudent(Student student) {
String sql = "insert into student (name,age) values (?,?)";
jdbcTemplate.update(sql,new Object[]{student.getName(),student.getAge()});
}
}
在beans.xml注入实体
第三种就是spring data
痛点：数据实现层的代码虽然少了，但注入模板也存在重复，分页等通用功能还需要开发，等等
思路：前面两种方式，都需要自己在数据库中手动建表，springdata可以实现实体与表映射，直接写实体类即可，映射通过@注解实现
只需要写接口，写方法，不需要写实现类-
实现：
pom.xml添加mysql驱动包org.springframework.data spring-data-jpa 1.8.0.RELEASE org.hibernate hibernate-entitymanager 4.3.6.Final
写resources/beans-new.xml配置
org.hibernate.cfg.ImprovedNamingStrategy
org.hibernate.dialect.MySQL5InnoDBDialect
true
true
update
写单元测试test.java
public class SpringDataTest {
private ApplicationContext context = null;
@Before
public void createContext(){
context = new ClassPathXmlApplicationContext("beans-new.xml");
}
@After
public void distoryContext(){
context = null;
}
@Test
public void testCreateTab(){
// 自动创建表
}
}
写业务代码
之前的事务是靠代码维护的，现在要交给框架维护，我们需要配置