一.导学
什么是SpringData？
主旨：提供一个熟悉的、一致的，基于Spring框架的数据访问框架。简化数据库的访问官网 https://spring.io/projects/spring-data
Spring Data包含多个子项目
Spring Data JPA:减少我们数据访问层的开发量Spring Data Mongo DBSpring Data RedisSpring Data Solr
二.使用传统方式访问数据库
使用JDBC访问数据库使用Spring提供的JdbcTemplate访问数据库
1.使用JDBC访问数据库
创建一个maven项目,导入依赖
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- 数据库驱动依赖 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
<!-- 单元测试依赖 -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>
开发JDBCUtil工具类
获取Connection关闭Connection、Statement、ResultSet
public class JDBCUtils {
public static Connection getConnection() throws Exception {
//不建议这种硬编码
/*
String url = "jdbc:mysql:///springdata";
String user = "root";
String password = "123456";
String driverClass = "com.mysql.jdbc.Driver";*/
InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(in);
String url = properties.getProperty("jdbc.url");
String user = properties.getProperty("jdbc.user");
String password = properties.getProperty("jdbc.password");
String driverClass = properties.getProperty("jdbc.driverClass");
Class.forName(driverClass);
return DriverManager.getConnection(url,user,password);
}
public static void release(Connection connection, Statement statement, ResultSet resultSet){
if(connection!=null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(statement!=null){
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
db.properties
jdbc.url=jdbc:mysql:///springdata
jdbc.user=root
jdbc.password=123456
jdbc.driverClass=com.mysql.jdbc.Driver
对象模型(实体类)
创建一个student表(id,name,age)id为主键 自增
public class Student {
private int id;
private String name;
private int age;
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
'}';
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
DAO接口
public interface StudentDao {
//查询所有的学生信息
List<Student> findAll();
//添加一个学生
void save(Student student);
}
DAO实现类
public class StudentDaoImpl implements StudentDao {
public List<Student> findAll() {
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
List<Student> students = new ArrayList<Student>();
String sql = "select *from student";
try {
connection = JDBCUtils.getConnection();
statement = connection.createStatement();
resultSet = statement.executeQuery(sql);
while(resultSet.next()){
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
int age = resultSet.getInt("age");
Student student = new Student();
student.setId(id);
student.setName(name);
student.setAge(age);
students.add(student);
}
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtils.release(connection,statement,resultSet);
}
return students;
}
public void save(Student student) {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
String sql = "insert into student(name,age) values (?,?)";
try {
connection = JDBCUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1,student.getName());
preparedStatement.setInt(2,student.getAge());
preparedStatement.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
}finally {
JDBCUtils.release(connection,preparedStatement,resultSet);
}
}
}
DAO接口测试类
public class StudentDaoImplTest {
@Test
public void findAllTest(){
StudentDao studentDao = new StudentDaoImpl();
List<Student> students = studentDao.findAll();
for(Student student:students){
System.out.println(student);
}
}
@Test
public void save(){
StudentDao studentDao = new StudentDaoImpl();
Student student = new Student();
student.setName("test1");
student.setAge(19);
studentDao.save(student);
}
}
2.使用Spring提供的JdbcTemplate访问数据库
添加依赖
<!-- spring jdbc -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
<!-- spring context -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.1.5.RELEASE</version>
</dependency>
创建配置文件类(视频中用的是xml配置 这里我改用注解)配置DataSource、JdbcTemplate和Spring注解扫描
@Configuration //申明为配置类
@ComponentScan("com.playmaker") //扫描这个包下的
public class SpringConfig {
@Autowired
private SpringJdbcProperties springJdbcProperties;
@Bean
public DriverManagerDataSource getDriverManagerDataSource(){
DriverManagerDataSource driverManagerDataSource = new DriverManagerDataSource();
driverManagerDataSource.setDriverClassName(springJdbcProperties.getDriverClass());
driverManagerDataSource.setUrl(springJdbcProperties.getUrl());
driverManagerDataSource.setUsername(springJdbcProperties.getUser());
driverManagerDataSource.setPassword(springJdbcProperties.getPassword());
return driverManagerDataSource;
}
@Bean
public JdbcTemplate getJdbcTemplate(){
JdbcTemplate jdbcTemplate = new JdbcTemplate();
jdbcTemplate.setDataSource(getDriverManagerDataSource());
return jdbcTemplate;
}
}
上面这段相当于xml中这样配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
<property name="url" value="jdbc:mysql:///spring_data"/>
</bean>
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
@PropertySource(value = "classpath:db.properties") //位置
@Component
public class SpringJdbcProperties {
@Value("${jdbc.url}")
private String url;
@Value("${jdbc.user}")
private String user;
@Value("${jdbc.password}")
private String password;
@Value("${jdbc.driverClass}")
private String driverClass;
@Override
public String toString() {
return "SpringJdbcProperties{" +
"url='" + url + '\'' +
", user='" + user + '\'' +
", password='" + password + '\'' +
", driverClass='" + driverClass + '\'' +
'}';
}
public String getUrl() {
return url;
}
public String getUser() {
return user;
}
public String getPassword() {
return password;
}
public String getDriverClass() {
return driverClass;
}
}
DAO接口实现
@Repository//让Spring创建UserDaoImpl实例,相当于在配置文件去配置bean一样,这里也可以设置名字
public class StudentDaoSpringJdbcImpl implements StudentDao {
@Autowired
private JdbcTemplate jdbcTemplate;
public List<Student> findAll() {
List<Student> students = new ArrayList<Student>();
String sql = "select id,name,age from student";
List<Map<String,Object>> list_map = jdbcTemplate.queryForList(sql);
for(Map<String,Object> map:list_map){
int id = Integer.valueOf(map.get("id").toString());
String name = String.valueOf(map.get("name"));
int age = Integer.valueOf(map.get("age").toString());
Student student = new Student();
student.setId(id);
student.setName(name);
student.setAge(age);
students.add(student);
}
return students;
}
public void save(Student student) {
String sql = "insert into student(name,age) values(?,?)";
jdbcTemplate.update(sql,new Object[]{student.getName(),student.getAge()});
}
}
DAO接口测试类
public class StudentDaoSpringJdbcImplTest {
private ApplicationContext applicationContext = null;
private StudentDao studentDao ;
@Before
public void init(){
applicationContext = new AnnotationConfigApplicationContext(SpringConfig.class);
studentDao = applicationContext.getBean(StudentDao.class);
System.out.println("init...");
}
@After
public void destroy(){
applicationContext=null;
System.out.println("destroy...");
}
@Test
public void findAllTest(){
List<Student> students = studentDao.findAll();
for(Student student:students){
System.out.println(student);
}
}
@Test
public void save(){
Student student = new Student();
student.setName("test1");
student.setAge(19);
studentDao.save(student);
}
}
弊端分析 无论是原始JDBC连接数据库还是Spring提供的JdbcTemplate来处理,DAO里面代码量太多,DAO的实现有很多重复代码,如果你想实现更复杂的分页功能之类的,还需要写更大量的代码,学习了Spring data你就会知道它的强大了
