jdbc代码封装

首先创建数据库表，插入2条测试数据

DAO

package com.godinsec;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

/**
 * 访问数据的DAO接口 T:DAO处理的实体类的类型
 */
public interface DAO {
    /**
     * 批量处理的方法
     */
    void batch(Connection connection, String sql, Object[]... args)
            throws SQLException;

    /**
     * 返回具体的一个值：总人数，某个人的信息，平均工资
     */
     E getForValue(Connection connection, String sql, Object... args)
            throws SQLException;

    /**
     * 返回一个T的集合
     * 
     * @return
     */
    List getForList(Connection connection, String sql, Object... args)
            throws SQLException;

    /**
     * 返回一个T的对象
     * 
     * @return
     */
    T get(Connection connection, String sql, Object... args)
            throws SQLException;

    /**
     * 增、删、改操作
     */
    void update(Connection connection, String sql, Object... args)
            throws SQLException;

    /**
     * 查询方法
     */
}

JDBCDAO

package com.godinsec;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

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;

public class JDBCDAO implements DAO{
    //QueryRunner是线程安全的
    private QueryRunner queryRunner = null;
    private Class type;
    public JDBCDAO(){
        queryRunner = new QueryRunner();
        type = ReflectionUtils.getSuperGenericType(getClass());
    }
    @Override
    public void batch(Connection connection, String sql, Object[]... args)
            throws SQLException {
        queryRunner.batch(connection, sql, args);
    }
    //已经实现
    @Override
    public  E getForValue(Connection connection, String sql, Object... args)
            throws SQLException {
        return (E) queryRunner.query(connection, sql, new ScalarHandler(), args);
    }
    //已经实现
    @Override
    public List getForList(Connection connection, String sql, Object... args)
            throws SQLException {
        return queryRunner.query(connection, sql, 
                new BeanListHandler<>(type), args);
    }
    //已经实现
    @Override
    public T get(Connection connection, String sql, Object... args)
            throws SQLException {
        return queryRunner.query(connection, sql, new BeanHandler<>(type), args);
    }
    //已经实现
    @Override
    public void update(Connection connection, String sql, Object... args)
            throws SQLException {
        queryRunner.update(connection, sql, args);
    }
}

CustomerDao

package com.godinsec;
public class CustomerDao extends JDBCDAO{

}

接下来看一个bean类Customer

    private Integer id;
    private String name;
    private String email;
    private Date birth;

最后看测试类的方法吧CustomerDaoTest

1、获取某个字段的值

@Test
    public void testGetForValue() {
        Connection connection = null;
        try {
            connection = JdbcTools.getConnection();
            String sql = "select id,name,email,birth from customer where name = ?";
            Object result = customerDao.getForValue(connection, sql,
                    "aaa");
            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JdbcTools.releaseDB(null, null, null, connection);
        }
    }

输出如下
1

2、获取某个对象

@Test
    public void testGet() {
        Connection connection = null;
        try {
            connection = JdbcTools.getConnection();
            String sql = "select id,name,email,birth from customer where id=?";
            Customer customer = customerDao.get(connection, sql, 1);
            System.out.println(customer);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JdbcTools.releaseDB(null, null, null, connection);
        }
    }

输出如下：

Customer [id=1, name=aaa, email=aaa, birth=2016-10-05]

3、获取某个对象集合列表

@Test
    public void testGetForList() {
        Connection connection = null;
        try {
            connection = JdbcTools.getConnection();
            String sql = "select id,name,email,birth from customer";

            List customers = customerDao.getForList(connection, sql);
            System.out.println(customers);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JdbcTools.releaseDB(null, null, null, connection);
        }
    }

[Customer [id=1, name=aaa, email=aaa, birth=2016-10-05], Customer [id=2, name=bbb, email=bbb, birth=2016-10-26]]

4、对数据库进行增删改操作

    @Test
    public void testUpdate() {
        Connection connection = null;
        try {
            connection = JdbcTools.getConnection();
            String sql = "insert into customer values(?,?,?,?)";
            // 使用其方法
            customerDao.update(connection, sql, 10, "ccc", "ccc",
                    "2011-10-20");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JdbcTools.releaseDB(null, null, null, connection);
        }
    }

再次查询数据库，记录增加一条

最后还有一个数据库工具类，以及一个反射工具类
JdbcTools

package com.godinsec;

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 javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcTools {
    // 开始事务
    public static void beginTx(Connection connection) {
        if (connection != null) {
            try {
                connection.setAutoCommit(false);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    // 回滚事务
    public static void rollback(Connection connection) {
        if (connection != null) {
            try {
                connection.close();
            } 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();
            }
        }
    }

    // 使用数据库链接池来获取数据库链接--私有静态
    private static DataSource dataSource = null;
    // 数据库连接池只需要初始化一次就够了，因为一个项目只需要一个连接池就够了
    static {
        dataSource = new ComboPooledDataSource("helloc3p0");
    }

    public static Connection getConnection() throws Exception {
        return dataSource.getConnection();
    }

    // 获取连接
    public static Connection getConnection1() throws Exception {
        String user = "root";
        String password = "root";
        String jdbcUrl = "jdbc:mysql:///mydatabase";
        String driverClass = "com.mysql.jdbc.Driver";
        Class.forName(driverClass);
        Connection connection = DriverManager.getConnection(jdbcUrl, user,
                password);
        return connection;
    }

    // 关闭资源
    public static void releaseDB(ResultSet resultSet,
            PreparedStatement preparedStatement, Statement statement,
            Connection connection) {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (preparedStatement != null) {
            try {
                preparedStatement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (connection != null) {
            try {
                // 数据库链接池的connection对象并不是真的进行关闭
                // 而是把链接归还到数据库连接池中
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

ReflectionUtils

package com.godinsec;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * 反射的 Utils 函数集合
 * 提供访问私有变量, 获取泛型类型 Class, 提取集合中元素属性等 Utils 函数
 * @author Administrator
 *
 */
public class ReflectionUtils {


    /**
     * 通过反射, 获得定义 Class 时声明的父类的泛型参数的类型
     * 如: public EmployeeDao extends BaseDao
     * @param clazz
     * @param index
     * @return
     */
    @SuppressWarnings("unchecked")
    public static Class getSuperClassGenricType(Class clazz, int index){
        Type genType = clazz.getGenericSuperclass();

        if(!(genType instanceof ParameterizedType)){
            return Object.class;
        }

        Type [] params = ((ParameterizedType)genType).getActualTypeArguments();

        if(index >= params.length || index < 0){
            return Object.class;
        }

        if(!(params[index] instanceof Class)){
            return Object.class;
        }

        return (Class) params[index];
    }

    /**
     * 通过反射, 获得 Class 定义中声明的父类的泛型参数类型
     * 如: public EmployeeDao extends BaseDao
     * @param 
     * @param clazz
     * @return
     */
    @SuppressWarnings("unchecked")
    public static Class getSuperGenericType(Class clazz){
        return getSuperClassGenricType(clazz, 0);
    }

    /**
     * 循环向上转型, 获取对象的 DeclaredMethod
     * @param object
     * @param methodName
     * @param parameterTypes
     * @return
     */
    public static Method getDeclaredMethod(Object object, String methodName, Class[] parameterTypes){

        for(Class superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
            try {
                //superClass.getMethod(methodName, parameterTypes);
                return superClass.getDeclaredMethod(methodName, parameterTypes);
            } catch (NoSuchMethodException e) {
                //Method 不在当前类定义, 继续向上转型
            }
            //..
        }

        return null;
    }

    /**
     * 使 filed 变为可访问
     * @param field
     */
    public static void makeAccessible(Field field){
        if(!Modifier.isPublic(field.getModifiers())){
            field.setAccessible(true);
        }
    }

    /**
     * 循环向上转型, 获取对象的 DeclaredField
     * @param object
     * @param filedName
     * @return
     */
    public static Field getDeclaredField(Object object, String filedName){

        for(Class superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
            try {
                return superClass.getDeclaredField(filedName);
            } catch (NoSuchFieldException e) {
                //Field 不在当前类定义, 继续向上转型
            }
        }
        return null;
    }

    /**
     * 直接调用对象方法, 而忽略修饰符(private, protected)
     * @param object
     * @param methodName
     * @param parameterTypes
     * @param parameters
     * @return
     * @throws InvocationTargetException 
     * @throws IllegalArgumentException 
     */
    public static Object invokeMethod(Object object, String methodName, Class [] parameterTypes,
            Object [] parameters) throws InvocationTargetException{

        Method method = getDeclaredMethod(object, methodName, parameterTypes);

        if(method == null){
            throw new IllegalArgumentException("Could not find method [" + methodName + "] on target [" + object + "]");
        }

        method.setAccessible(true);

        try {
            return method.invoke(object, parameters);
        } catch(IllegalAccessException e) {
            System.out.println("不可能抛出的异常");
        } 

        return null;
    }

    /**
     * 直接设置对象属性值, 忽略 private/protected 修饰符, 也不经过 setter
     * @param object
     * @param fieldName
     * @param value
     */
    public static void setFieldValue(Object object, String fieldName, Object value){
        Field field = getDeclaredField(object, fieldName);

        if (field == null)
            throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");

        makeAccessible(field);

        try {
            field.set(object, value);
        } catch (IllegalAccessException e) {
            System.out.println("不可能抛出的异常");
        }
    }

    /**
     * 直接读取对象的属性值, 忽略 private/protected 修饰符, 也不经过 getter
     * @param object
     * @param fieldName
     * @return
     */
    public static Object getFieldValue(Object object, String fieldName){
        Field field = getDeclaredField(object, fieldName);

        if (field == null)
            throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");

        makeAccessible(field);

        Object result = null;

        try {
            result = field.get(object);
        } catch (IllegalAccessException e) {
            System.out.println("不可能抛出的异常");
        }

        return result;
    }
}

c3p0-config.xml

    

        
        root
        root
        com.mysql.jdbc.Driver
        jdbc:mysql:///mydatabase

        
        5
        
        5
        
        5
        
        10

        
        20
        
        5