对比传统方式访问数据库和SpringData访问数据库

我们在写代码的时候应该一边写一边测试，这样的话可以尽快的找到错误，在代码写多了之后去找错误的话不容易给错误定位

传统方式访问数据库

1：创建一个Maven web项目

2：修改pom.xml为以下内容

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.gx</groupId>
  <artifactId>SpringData</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringData Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>SpringData</finalName>
  </build>
</project>

3：创建一个数据库表User，包括id，name，age三个字段，并向其中添加数据

4：创建一个配置文件db.properties，用于存放所有和数据库有关的配置

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3307/test
jdbc.username=root
jdbc.password=root

5：开发一个JDBC相关工具类com.gx.help.JdbcUtil

package com.gx.help;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/**
 * 这是一个JDBC工具类
 * @author Administrator
 *
 *包含的内容
 *1：获取Connection
 *2：释放资源（关闭Connection，Statement（PrepareStatement），ResultSet）
 */
public class JdbcUtil {
    /**
     * 获取Connection
     * @return 返回所获得的JDBC的Connection
     * @throws SQLException
     * @throws ClassNotFoundException
     * @throws IOException
     */
    public static Connection getConnection() throws SQLException, ClassNotFoundException, IOException{
        //从配置文件获取数据
        InputStream inputStream = JdbcUtil.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();
        properties.load(inputStream);
        //驱动程序名
        String driver=properties.getProperty("jdbc.driver");
        //url指向要访问的数据库名
        String url=properties.getProperty("jdbc.url");
        //MySQL配置时的用户名和密码
        String username=properties.getProperty("jdbc.username");
        String password=properties.getProperty("jdbc.password");
        Class.forName(driver);
        Connection conn = DriverManager.getConnection(url,username,password);
        return conn;
    }
    /**
     * 释放资源（使用Statement的情况下）
     * @param resultSet
     * @param statement
     * @param connection
     */
    public static void close(ResultSet resultSet,Statement statement,Connection connection){
        if(resultSet!=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(statement!=null){
            try {
                statement.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
    /**
     * 释放资源（使用PrepareStatement的情况下）
     * @param resultSet
     * @param preparedStatement
     * @param connection
     */
    public static void close(ResultSet resultSet,PreparedStatement preparedStatement,Connection connection){
        if(resultSet!=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(preparedStatement!=null){
            try {
                preparedStatement.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(connection!=null){
            try {
                connection.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

5：创建对象模型com.gx.domain.User

package com.gx.domain;

public class User {
    private int id;
    private String name;
    private int 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;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
    }

}

6：创建Dao的接口com.gx.dao.UserDao

package com.gx.dao;

import java.util.List;

import com.gx.domain.User;
/**
 * UserDao访问接口
 * @author Administrator
 *
 */
public interface UserDao {
    //查询所有用户
    public List<User> finaAll();
}

7：创建Dao的实现类com.gx.dao.impl.UserDaoImpl

package com.gx.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.gx.dao.UserDao;
import com.gx.domain.User;
import com.gx.help.JdbcUtil;
/**
 * UserDao访问接口实现类，这个实现类通过最原始的JDBC的操作实现
 * @author Administrator
 *
 */
public class UserDaoImpl implements UserDao{
    /**
     * 查询所有学生
     */
    public List<User> finaAll(){
        List<User> users = new ArrayList<User>();
        Connection conn=null;
        PreparedStatement preparedStatement = null;
        ResultSet result = null;
        try {
            String sql = "select * from user";
            conn = JdbcUtil.getConnection();
            preparedStatement = conn.prepareStatement(sql);
            result = preparedStatement.executeQuery();
            while(result.next()){
                User user = new User();
                user.setId(result.getInt("id"));
                user.setName(result.getString("name"));
                user.setAge(result.getInt("age"));
                users.add(user);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally{
            JdbcUtil.close(result, preparedStatement, conn);
        }
        return users;
    }
}

8：在JDBC相关工具类com.gx.help.JdbcUtil里面添加测试方法

    @Test
    public void testUserQuery(){
        UserDao udao = new UserDaoImpl();
        List<User> users = udao.finaAll();
        for(User user:users){
            System.out.println(user.toString());
        }
    }

9：运行测试类

10：添加save方法并测试

UserDao里面的代码

    //添加学生
    public void save(User user);

UserDaoImpl里面的代码

/**
     * 添加学生
     */
    public void save(User user){
        Connection conn=null;
        PreparedStatement preparedStatement = null;
        ResultSet result = null;
        try {
            String sql = "insert into user(id,name,age) value(?,?,?)";
            conn = JdbcUtil.getConnection();
            preparedStatement = conn.prepareStatement(sql);
            preparedStatement.setInt(1,user.getId());
            preparedStatement.setString(2,user.getName());
            preparedStatement.setInt(3,user.getAge());
            preparedStatement.executeUpdate();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally{
            JdbcUtil.close(result, preparedStatement, conn);
        }
    }

JdbcUtilTest里面的代码

　　@Test
    public void testUserSave(){
        UserDao udao = new UserDaoImpl();
        User user = new User();
        user.setAge(12);
        user.setId(6);
        user.setName("minuobaci");
        udao.save(user);
    }

测试结果

---

---

---

传统方式访问数据库的第二种方式（使用spring框架内置jdbc模板）

1：创建Maven项目

2：创建一个数据库表User，包括id，name，age三个字段，并向其中添加数据

3：修改pom.xml配置文件为以下内容

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.gx</groupId>
  <artifactId>SpringData</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringData Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>4.3.5.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.5.RELEASE</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>SpringData</finalName>
  </build>
</project>

4：在src/main/resources里面添加spring配置文件beans.xml（名字是随便取的）

<?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://localhost:3307/test" />
    </bean>

</beans>

5：添加测试类com.gx.JdbcUtilTest测试配置文件是否正确

package com.gx;

import javax.sql.DataSource;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import junit.framework.Assert;

public class JdbcUtilTest {
    private ApplicationContext ctx = null;
    @Before
    public void setup(){
        System.out.println("setup is working......");
        ctx = new ClassPathXmlApplicationContext("beans.xml");
    }
    @After
    public void destory(){
        ctx = null;
        System.out.println("destory is working......");
    }
    @Test
    public void testDataSource(){
        System.out.println("testDataSource is working......");
        DataSource dataSource = (DataSource) ctx.getBean("dataSource");//dataSource是配置文件里面beans的id
        Assert.assertNotNull(dataSource);
    }
}

6：运行测试类

7：继续注入JdbcTemplate（在beans.xml文件里面添加以下代码）

　　<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <!-- 因为是引用，所以不能用value，需要用ref -->
        <property name="dataSource" ref="dataSource" />
    </bean>

8：同理，测试一下是否正确（在测试类com.gx.JdbcUtilTest里面添加以下代码）

　　@Test
    public void testJdbcTemplate(){
        System.out.println("testJdbcTemplate is working......");
        JdbcTemplate jdbcTemplate = (JdbcTemplate) ctx.getBean("jdbcTemplate");
        Assert.assertNotNull(jdbcTemplate);
    }

10：测试结果

11：定义接口UserDao（可以直接使用“传统方式访问数据库”里面的UserDao）

12：创建UserDao的实现类UserDaoImpl

package com.gx.dao.impl;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowCallbackHandler;

import com.gx.dao.UserDao;
import com.gx.domain.User;
/**
 * UserDao访问接口实现类，这个实现类通过最Spring jdbc的方式操作
 * @author Administrator
 *
 */
public class UserDaoImpl implements UserDao{
    //注入jdbcTemplate
    private JdbcTemplate jdbcTemplate;
    public JdbcTemplate getJdbcTemplate() {
        return jdbcTemplate;
    }
    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }
    /**
     * 查询所有学生
     */
    public List<User> finaAll(){
        final List<User> users = new ArrayList<User>();
        String sql = "select * from user";

        jdbcTemplate.query(sql, new RowCallbackHandler(){

            public void processRow(ResultSet result) throws SQLException {
                User user = new User();
                user.setId(result.getInt("id"));
                user.setName(result.getString("name"));
                user.setAge(result.getInt("age"));
                users.add(user);
            }

        });

        return users;
    }
    /**
     * 添加学生
     */
    public void save(User user){
        String sql = "insert into user(id,name,age) value(?,?,?)";
        jdbcTemplate.update(sql,new Object[]{user.getId(),user.getName(),user.getAge()});
    }
}

13：因为UserDAOImpl是使用spring Jdbc的方式来实现的，所以我们必须将UserDAOImpl配置到beans.xml文件里面去，并将我们使用到的JdbcTemplate注入其中，否则UserDAOImpl将无法使用JdbcTemplate

    <bean id="UserDao" class="com.gx.dao.impl.UserDaoImpl">
        <property name="jdbcTemplate" ref="jdbcTemplate" />
    </bean>

14：编写测试方法（修改测试类com.gx.JdbcUtilTest为以下代码）

package com.gx;

import java.util.List;

import javax.sql.DataSource;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.jdbc.core.JdbcTemplate;

import com.gx.dao.UserDao;
import com.gx.domain.User;

import junit.framework.Assert;

public class JdbcUtilTest {
    private ApplicationContext ctx = null;
    private UserDao userDao = null;
    @Before
    public void setup(){
        System.out.println("setup is working......");
        ctx = new ClassPathXmlApplicationContext("beans.xml");
        userDao = (UserDao)ctx.getBean("UserDao");//此处的UserDao对应beans.xml文件里面的bean的ID
    }
    @After
    public void destory(){
        ctx = null;
        System.out.println("destory is working......");
    }

    @Test
    public void testQuery(){
        List<User> users = userDao.finaAll();
        for(User user:users){
            System.out.println(user);
        }
    }

    @Test
    public void testSave(){
        User user = new User();
        user.setAge(12);
        user.setId(7);
        user.setName("minuo");
        userDao.save(user);
    }
}

15：测试查询的结果

16：测试添加的结果

我们可以看到，上面两种方法的对比中第二种方法：使用spring框架内置jdbc模板。使用的代码更少，更简单，因为像Connection等操作都不在需要我们来做了，他们都交由spring来管理了

两种弊端分析

1：两个方法的Dao涉及到非常多的代码

2：Dao的实现由很多重复的代码

3：如果要开发分页这些的方法还要重新封装

---

---

---

使用SpringData访问数据库

1：创建Maven项目修改pom.xml配置文件为以下代码

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.gx</groupId>
  <artifactId>SpringData</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>SpringData Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.0.1</version>
        <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>4.3.5.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.5.RELEASE</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework.data/spring-data-jpa -->
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-jpa</artifactId>
        <version>1.8.0.RELEASE</version>
    </dependency>
    <!-- hibernate-entity -->
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>4.3.6.Final</version>
    </dependency>
  </dependencies>
  <build>
    <finalName>SpringData</finalName>
  </build>
</project>

2：创建一个数据库表User，包括id，name，age三个字段，并向其中添加数据

3：创建一个配置文件spring-data-beans.xml内容如下

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">

    <!-- 配置数据源 -->
    <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://localhost:3307/test" />
    </bean>

    <!-- 配置EntityManagerFactory -->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 设置jpa适配器 -->
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"/>
        </property>
        <!-- 采用注解的方式，扫描包下面的java类 -->
        <property name="packagesToScan" value="com.gx"/>
        <!-- jpa的相关配置 -->
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.ejb.naming_strategy">org.hibernate.cfg.ImprovedNamingStrategy</prop>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</prop>
                <prop key="hibernate.show_sql">true</prop><!--执行的时候是否显示SQL-->
                <prop key="hibernate.format_sql">true</prop><!--执行的时候SQL是否格式化-->
                <prop key="hibernate.hbm2ddl.auto">update</prop><!--如果没有是否创建-->
            </props>
        </property>
    </bean>

    <!--配置事务管理器-->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!--配置支持注解的事务-->
    <tx:annotation-driven transaction-manager="transactionManager"/>

    <!--配置spring data 需要扫描的包-->
    <jpa:repositories base-package="com.gx" entity-manager-factory-ref="entityManagerFactory"/>

    <!--在这个配置里面的内容spring都能够自动找到，更方便-->
    <context:component-scan base-package="com.gx"/>

</beans>

4：创建对象模型com.gx.domain.User

package com.gx.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
/*
 * 这个Entity的注解会告诉配置文件这是一个实体类
 * 配置文件会根据EntityManagerFactory来判断是否有这个表
 * 如果没有会字动生成
 */
@Entity
public class User {
    /* 最好使用封装之后的类型
     * 因为在后面的类UserRepository适用的时候会继承泛型类Repository<User,Integer>，这里的Integer就是主键Id的类型
     */
    private Integer id;
    private String name;
    private Integer age;
    @GeneratedValue//这个注解是告诉配置文件这个id是自增的
    @Id//这个注解是告诉配置文件这是一个id
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    /*这个注解是设置表user里面的name字段的长度为20，默认不为空
     * 如果不设置的话默认是255
     */
    @Column(length=20,nullable=false)
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
    }

}

5：定义接口com.gx.repository.UserRepository用于访问数据库

package com.gx.repository;

import java.util.List;

import org.springframework.data.repository.Repository;

import com.gx.entity.User;

public interface UserRepository extends Repository<User, Integer>{
    //查找全部学生信息
    public List<User> findAll();
    //保存学生信息
    public void save(User user);
}

6：添加测试类com.gx.SpringData

package com.gx;

import java.util.List;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.gx.entity.User;
import com.gx.repository.UserRepository;

public class SpringData {
    //获取上下文
    private ApplicationContext ctx = null;
    private UserRepository userRepository = null;
    @Before
    public void setup(){
        System.out.println("setup is working......");
        ctx = new ClassPathXmlApplicationContext("spring-data-beans.xml");
        userRepository = ctx.getBean(UserRepository.class);
    }
    @After
    public void destory(){
        ctx = null;
        System.out.println("destory is working......");
    }

    @Test
    public void testSave(){
        User user = new User();
        user.setAge(12);
        user.setId(2);
        user.setName("baci");
        userRepository.save(user);
        System.out.println("testSave is working......");
    }

    @Test
    public void testFindAll(){
        List<User> users = userRepository.findAll();
        for(User user:users){
            System.out.println(user);
        }
    }
}

7：运行testSave测试save方法

7.1：控制台

7.2：数据库

8：运行testFindAll测试findAll方法

关于spring data的更新在

http://www.cnblogs.com/minuobaci/p/7553118.html