JDBC技术总结
一、导包
二、配置文件
1. jdbc.properties
driver=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql://127.0.0.1:3306/test
user=root
password=root2.dbcp.properties
username=root
password=root
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/test
initialSize=10
maxTotal=50
minIdle=5
maxWaitMillis=50003.c3p0-config.xml
root
root
com.mysql.jdbc.Driver
jdbc:mysql://127.0.0.1:3306/test
5
5
5
10
20
5
三、JBDC工具类
package com.jdbc.tools;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.apache.commons.beanutils.BeanUtils;
import javax.sql.DataSource;
import java.sql.*;
import java.util.HashMap;
import java.util.Map;
/**
* JDBC 的工具类，其中封装了一些工具方法
*
* @author Administrator
*/
public class JDBCTools {
//（开始事务）关闭事务自动提交
public static void beginTX(Connection connection) {
if (connection != null) {
try {
connection.setAutoCommit(false);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//提交事务
public static void commit(Connection connection) {
if (connection != null) {
try {
connection.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
//回滚事务
public static void rollback(Connection connection) {
if (connection != null) {
try {
connection.rollback();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
private static DataSource dataSource = null;
static {
dataSource = new ComboPooledDataSource("c3p0");
}
/**
* 1.获取连接的方法
* 通过读取配置文件从数据库服务器获取一个连接
*
* @return
* @throws Exception
*/
public static Connection getConnection() throws Exception {
return dataSource.getConnection();
}
/**
* 2.关闭 Statement 、ResultSet 和 Connection 连接
*
* @param statement
* @param connection
*/
public static void release(ResultSet rs, Statement statement, Connection connection) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
* 3.通用更新方法
*
* @throws SQLException
*/
public static void update(String sql) {
//1.获取数据库连接
Connection connection = null;
Statement statement = null;
try {
connection = JDBCTools.getConnection();
statement = connection.createStatement();
statement.executeUpdate(sql);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
JDBCTools.release(null, statement, connection);
}
}
/**
* 通用更新方法升级
*/
public static void update(String sql, Object... args) {
Connection connection = null;
PreparedStatement preparedStatement = null;
try {
connection = JDBCTools.getConnection();
preparedStatement = (PreparedStatement) connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
preparedStatement.executeUpdate();
} catch (Exception e) {
} finally {
JDBCTools.release(null, preparedStatement, connection);
}
}
/**
* 通用查询方法
*/
public static T search(Class clazz, String sql, Object... args) {
T entity = null;
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
//1.得到ResulSet对象
connection = JDBCTools.getConnection();
preparedStatement = (PreparedStatement) connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
resultSet = preparedStatement.executeQuery();
//2.得到 ResultSetMeteData 对象
ResultSetMetaData rSetMetaData = (ResultSetMetaData) resultSet.getMetaData();
//3.创建一个Map对象，键：SQL查询列的列的别名 值：列的值
Map values = new HashMap();
//4.处理结果集，利用ResutSetMeteData 填充3对应的Map对象
while (resultSet.next()) {
//打印每一列的列名
for (int i = 0; i < rSetMetaData.getColumnCount(); i++) {
String columnLabel = rSetMetaData.getCatalogName(i + 1);
Object columnValue = resultSet.getObject(columnLabel);
values.put(columnLabel, columnValue);
}
}
//5.若Map不为空集，利用反射创建calzz 对应的对象,
if (values != null) {
Object object = clazz.newInstance();
//遍历Map 对象，利用反射为Class对象的对应属性值赋值
for (Map.Entry entry : values.entrySet()) {
String fieldName = entry.getKey();
Object fieldValue = entry.getValue();
// ReflectionUtils.setFieldValue(object, fieldName, fieldValue);
BeanUtils.setProperty(object, fieldName, fieldValue);
}
//返回对象
return (T) object;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCTools.release(null, preparedStatement, connection);
}
return null;
}
}
四、DAO设计模式
1.customer类（与数据库中customers表对应）
package com.jdbc.study;
import java.sql.Date;
/**
* @author
* @create 2020-04-12 17:54
*/
public class Customer {
private Integer id;
private String name;
private String email;
private Date brith;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Date getBrith() {
return brith;
}
public void setBrith(Date brith) {
this.brith = brith;
}
public Customer(Integer id, String name, String email, Date brith) {
this.id = id;
this.name = name;
this.email = email;
this.brith = brith;
}
public Customer() {
}
@Override
public String toString() {
return "Customer{" +
"id=" + id +
", name='" + name + '\'' +
", email='" + email + '\'' +
", brith=" + brith +
'}'+'\n';
}
}
2.DAO接口
package com.jdbc.tools;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
/**
* 访问数据的 DAO 接口
* 里边定义好访问数据表的各种方法
*
* @param T :DAO 处理的实体类的类型
* @author
* @create 2020-04-13 15:59
*/
public interface DAO {
/**
* 批量处理方法
*
* @param connection 数据库连接
* @param sql SQL 语句
* @param args 填充占位符的Object [] 类型的可变参数
*/
void batch(Connection connection, String sql, Object[]... args) throws SQLException;
/**
* 返回具体的一个值 例如总人数，email
*
* @param connection 数据库连接
* @param sql SQL 语句
* @param args 填充占位符的可变参数
* @param
* @return
* @throws SQLException
*/
E getForValue(Connection connection, String sql, Object... args) throws SQLException;
/**
* 返回 T 的集合
*
* @param connection 数据库连接
* @param sql SQL 语句
* @param args 填充占位符的可变参数
* @return
* @throws SQLException
*/
List getForList(Connection connection, String sql, Object... args) throws SQLException;
/**
* 返回一个 T 的对象
*
* @param connection 数据库连接
* @param sql SQL 语句
* @param args 填充占位符的可变参数
* @return
* @throws SQLException
*/
T get(Connection connection, String sql, Object... args) throws SQLException;
/**
* INSERT,UPDATE,DELETE
*
* @param connection : 数据库连接
* @param sql :SQL 语句
* @param args :填充占位符的可变参数
*/
void update(Connection connection, String sql, Object... args) throws SQLException;
}
3.JdbcDaoImpl 实现类
package com.jdbc.tools;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
/**
* 使用 QueryRunner 提供其具体实现类
* @param 子类需传入的泛型
*/
public class JdbcDaoImpl implements DAO {
private QueryRunner queryRunner = null;
private Class type;
public JdbcDaoImpl(){
queryRunner = new QueryRunner();
type = ReflectionUtils.getSuperGenericType(getClass());
}
@Override
public void batch(Connection connection, String sql, Object[]... args) throws SQLException {
queryRunner.batch(connection, sql, args);
}
@Override
public E getForValue(Connection connection, String sql, Object... args) throws SQLException {
return (E)queryRunner.query(connection,sql,new ScalarHandler(),args);
}
@Override
public List getForList(Connection connection, String sql, Object... args) throws SQLException {
return (List)queryRunner.query(connection, sql, new BeanListHandler<>(type),args);
}
@Override
public T get(Connection connection, String sql, Object... args) throws SQLException {
return queryRunner.query(connection,sql,new BeanHandler<>(type),args);
}
@Override
public void update(Connection connection, String sql, Object... args) throws SQLException {
queryRunner.update(connection, sql, args);
}
}
4.CustomerDao类（继承JdbcDaoImpl类）
package com.jdbc.tools;
import com.jdbc.study.Customer;
import java.sql.Connection;
import java.sql.SQLException;
/**
* @author
* @create 2020-04-13 16:14
*/
public class CustomerDao extends JdbcDaoImpl {
}
测试：测试其中的Get方法和GetForValue方法
package com.jdbc.test;
import com.jdbc.study.Customer;
import com.jdbc.tools.CustomerDao;
import com.jdbc.tools.JDBCTools;
import org.junit.Test;
import java.sql.Connection;
/**
* @author LIXICHEN
* @create 2020-04-13 16:22
*/
public class CustomerDaoTest {
CustomerDao customerDao = new CustomerDao();
@Test
public void testGetForValue(){
Connection connection = null;
try{
connection = JDBCTools.getConnection();
String sql = "SELECT name FROM customers WHERE id = ?";
String customer = customerDao.getForValue(connection,sql,5);
System.out.println(customer);
}catch(Exception e){
e.printStackTrace();
}finally{
JDBCTools.release(null,null,connection);
}
}
@Test
public void testGet(){
Connection connection = null;
try{
connection = JDBCTools.getConnection();
String sql = "SELECT * FROM customers WHERE id = ?";
Customer customer = customerDao.get(connection,sql,5);
System.out.println(customer);
}catch(Exception e){
e.printStackTrace();
}finally{
JDBCTools.release(null,null,connection);
}
}
}
测试结果
Get()方法
GetForValue()方法
