详解DBUtils工具的使用
DBUtils的使用
Commons DbUtils是Apache组织提供的一个对JDBC进行简单封装的开源工具类库，使用它能够简化JDBC应用程序的开发，同时也不会影响程序的性能
DBUtils简介
DBUtils是java编程中的数据库操作实用工具，小巧简单实用，
1.对于数据表的读操作，可以把结果转换成List，Array，Set等java集合，便于程序员操作
2.对于数据表的写操作，也变得很简单（只需写sql语句）
DBUtils包括的主要类
DbUtils类：启动类
ResultSetHandler接口：转换类型的接口
- ArrayHandler类：实现类，把记录转化为数组
- ArrayListHandler类：把记录转化为数组，并放入集合中
- ColumnListHandler类：获取某一列的数据。封装到List中
- ScalarHandler类：适合获取一行，一列的数据
- BeanHandler类：实现类，把记录转成对象
- BeanListHandler类：实现类，把记录转化为List，使记录为JavaBean类型的对象
QueryRunner类：执行SQL语句的类
DBUtils工具类的封装（实现对数据库的增删改查）
准备工作：
导入jar包 工具类 配置文件
commons-dbutils-1.6.jar
druid-1.1.5.jar
DruidUtils.java工具类
druid.properties配置文件
配置文件：
#连接设置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/myschool?useSSL=true&characterEncoding=utf8
username=root
password=root
#<!-- 初始化连接 -->
initialSize=20
#最大连接数量
maxActive=50
#<!-- 最小空闲连接 -->
minIdle=5
#<!-- 超时等待时间以毫秒为单位 6000毫秒/1000等于60秒 -->
maxWait=5000
创建类，把类中的属性和数据库中的属性对应
public class User implements Serializable {
private static final long serialVersionUID = 3567498598890692746L;
private Integer id;
private String username;
private String password;
private String phone;
public User() {
}
public User(Integer id, String username, String password, String phone) {
this.id = id;
this.username = username;
this.password = password;
this.phone = phone;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", phone='" + phone + '\'' +
'}';
}
把每次都需要进行的连接操作抽取出来，使用连接池，每次都从连接池中取连接，返回的参数，正好是DBUtils使用的参数
public class DataSourceUtils {
private static DruidDataSource dataSource;
static {
try {
Properties properties = new Properties();
InputStream is = DataSourceUtils.class.getClassLoader().getResourceAsStream("druid.properties");
properties.load(is);
dataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
e.printStackTrace();
}
}
public static DataSource getDataSource(){
return dataSource;
}
}
接口：
public interface UserDao {
//添加
void add(User user);
//修改
void Update(User user);
//删除
void Delete(Integer id);
//查询所有
public List<User> findAll();
//根据id查询某个人的数据
User findById(Integer id);
//获取数据个数
long getCount() throws SQLException;
//把查询的数据转换成一个数组
Object[] findArrayUser(Integer id);
//查询所有数据，把每条数据当成是一个对象，存入集合中
List<Object[]> findArrayList();
//查询一列的数据
List<String> findNames();
}
接口的实现类：
public class UserDaoImpl implements UserDao {
@Override
public void add(User user) {
//1.创建查询执行器，传入连接池，不用关闭
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
//2.执行
Object[] params = {
user.getId(), user.getUsername(), user.getPassword(), user.getPhone()};
try {
qr.update("insert into user(id,username,password,phone) values(?,?,?,?)", params);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("添加失败", e);
}
}
@Override
public void Update(User user) {
//1.创建查询执行器，传入连接池
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
//2.执行
Object[] params = {
user.getUsername(), user.getPassword(), user.getPhone(),user.getId()};
try {
qr.update("update user set username=?, password=?, phone=? where id=?", params);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("更新失败", e);
}
}
@Override
public void Delete(Integer id) {
//1.创建查询执行器，传入连接池
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
//2.执行
try {
qr.update("delete from user where id=?", id);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("删除失败", e);
}
}
@Override
public List<User> findAll() {
//1.创建查询
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
try {
//返回一个对象数组
List<User> list = qr.query("select * from user", new BeanListHandler<User>(User.class));
return list;
} catch (SQLException e) {
//e.printStackTrace();
throw new RuntimeException("查不到啊，老弟",e );
}
}
@Override
public User findById(Integer id) {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
try {
//返回一个对象
User user = qr.query("select * from user where id=?", new BeanHandler<User>(User.class),id);
//User user = qr.query(sql, new BeanHandler(User.class),id);
return user;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("查不到啊，老弟",e );
}
}
@Override
public long getCount() {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
Long count = null;
try {
//单行单列
count = (Long) qr.query("select count(*) from user", new ScalarHandler<>());
return count;
} catch (SQLException e) {
e.printStackTrace();
}
return -1;
}
@Override
public Object[] findArrayUser(Integer id) {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
try {
Object[] objects = qr.query("select * from user where id=?", new ArrayHandler(),id);
return objects;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("查询失败", e);
}
}
@Override
public List<Object[]> findArrayList() {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
try {
List<Object[]> list = qr.query("select * from user", new ArrayListHandler());
return list;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("查询失败", e);
}
}
@Override
public List<String> findNames() {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
try {
List<String> username = qr.query("select * from user", new ColumnListHandler<String>("username"));
return username;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("查询失败", e);
}
}
}
测试类：
public class UserDaoImplTest {
@Test
public void testAdd() {
UserDao userDao = new UserDaoImpl();
User user = new User(4,"诸葛亮", "0000", "120");
userDao.add(user);
System.out.println("添加成功");
}
@Test
public void testUpdate(){
UserDao userDao = new UserDaoImpl();
User user = new User(4,"诸葛亮", "55555", "120");
userDao.Update(user);
System.out.println("更新成功");
}
@Test
public void testDelete(){
UserDao userDao = new UserDaoImpl();
userDao.Delete(4);
System.out.println("删除成功");
}
@Test
public void testFindAll(){
UserDao userDao = new UserDaoImpl();
List<User> list = userDao.findAll();
for (User user : list) {
System.out.println(user.toString());
}
}
@Test
public void testFindById() {
UserDao userDao = new UserDaoImpl();
User user = userDao.findById(1);
System.out.println(user.toString());
}
@Test
public void testCount(){
UserDao userDao = new UserDaoImpl();
try {
long count = userDao.getCount();
System.out.println(count);
} catch (SQLException e) {
e.printStackTrace();
}
}
@Test
public void testArrayList() {
UserDao userDao = new UserDaoImpl();
List<Object[]> arrayList = userDao.findArrayList();
for (Object[] objects : arrayList) {
System.out.println(Arrays.toString(objects));
}
}
@Test
public void testArrayListUser() {
UserDao userDao = new UserDaoImpl();
Object[] user = userDao.findArrayUser(3);
for (Object o : user) {
System.out.println(o.toString());
}
}
@Test
public void testFindNames() {
UserDao userDao = new UserDaoImpl();
List<String> names = userDao.findNames();
for (String name : names) {
System.out.println(name);
}
}
}
【总结】：
/**
*
*对于增、删、改来说
* 步骤
* 1.创建查询执行器（QueryRunner），传入连接池
* 2.调用 查询执行器的 update()方法，传入 【相应的数据增、删、改语句】，和需要的 【参数】
*
* 对于查询来说
* 步骤：
* 1.创建查询执行器（QueryRunner），传入连接池
* 2.调用查询执行器的 query()方法，传入 【相应数据查询语句】，和相应的参数【参数传入想要得到的数据对应的类，和参数】
*/