java c3p0

c3p0的配置

1. 使用c3p0数据库连接池实现连接
   1.1. 需要引入c3p0 .jar 包
   1.2. 新建配置文件[src 目录下面新建c3p0-config.xml]
   <?xml version="1.0" encoding="UTF-8"?>

<c3p0-config>

<named-config name="mvcapp">    <property name="user">root</property>    <property name="password"></property>    <property name="driverClass">com.mysql.jdbc.Driver</property>    <property name="jdbcUrl">jdbc:mysql://localhost:3306/java</property>    <property name="acquireIncrement">5</property>    <property name="initialPoolSize">10</property>    <property name="minPoolSize">10</property>    <property name="maxPoolSize">50</property>    <property name="maxStatements">20</property>    <property name="maxStatementsPerConnection">5</property></named-config>

</c3p0-config>

JdbcUtils.java
负责连接数据库

package com.curtis.jdbc;

import java.sql.Connection;
import java.sql.SQLException;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils {

private static DataSource dataSource = null;static {    // 数据源只能被创建一次    // 这个mvcapp跟数据库连接池里面的对应    dataSource = new ComboPooledDataSource("mvcapp");}public static Connection getConnection() throws SQLException {    return dataSource.getConnection();}public static void releaseConnection(Connection connection) {    try {        if (connection != null) {            connection.close();        }    } catch (Exception e) {        e.printStackTrace();    }}

}

DAO.java[带泛型的参数]
接口：数据库交互用到方法[查询所有记录、查询单条记录、增删改、查询单个值...]
package com.curtis.dao;

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

public interface DAO<T> {

void batch(Connection connection, String sql, Object[]... args)        throws SQLException;// 查询单个值<E> E getValue(Connection connection, String sql, Object... args)        throws SQLException;// 查询所有数据List<T> getAllList(Connection connection, String sql, Object... args)        throws SQLException;// 查询一条数据T getOne(Connection connection, String sql, Object... args)        throws SQLException;// insert update deletevoid update(Connection connection, String sql, Object... args)        throws SQLException;

}

JdbcDaoImpl.java[带泛型的参数]
通过QueryRunner 实现DAO接口里面的方法
package com.curtis.dao;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
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 JdbcDaoImpl<T> implements DAO<T> {

private QueryRunner queryRunner = null;private Class<T> clazz;// 构造函数@SuppressWarnings("unchecked")public JdbcDaoImpl() {    queryRunner = new QueryRunner();    Type superClass = getClass().getGenericSuperclass();    if (superClass instanceof ParameterizedType) {        ParameterizedType parameterizedType = (ParameterizedType) superClass;        Type[] typeArgs = parameterizedType.getActualTypeArguments();        if (typeArgs != null && typeArgs.length > 0) {            if (typeArgs[0] instanceof Class) {                clazz = (Class<T>) typeArgs[0];            }        }    }}@Overridepublic void batch(Connection connection, String sql, Object[]... args)        throws SQLException {    queryRunner.batch(connection, sql, args);}@SuppressWarnings("unchecked")@Overridepublic <E> E getValue(Connection connection, String sql, Object... args)        throws SQLException {    return (E) queryRunner            .query(connection, sql, new ScalarHandler(), args);}@Overridepublic List<T> getAllList(Connection connection, String sql, Object... args)        throws SQLException {    return queryRunner.query(connection, sql, new BeanListHandler<>(clazz),            args);}@Overridepublic T getOne(Connection connection, String sql, Object... args)        throws SQLException {    return queryRunner.query(connection, sql, new BeanHandler<>(clazz),            args);}@Overridepublic void update(Connection connection, String sql, Object... args)        throws SQLException {    queryRunner.update(connection, sql, args);}

}

实体类继承JdbcDaoImpl.java，指明具体的实体
package com.curtis.table;

public class Student {

private int flow_id;private int type;private String id_card;private String student_name;private String location;private int grade;public int getFlow_id() {    return flow_id;}public void setFlow_id(int flow_id) {    this.flow_id = flow_id;}public int getType() {    return type;}public void setType(int type) {    this.type = type;}public String getId_card() {    return id_card;}public void setId_card(String id_card) {    this.id_card = id_card;}public String getStudent_name() {    return student_name;}public void setStudent_name(String student_name) {    this.student_name = student_name;}public String getLocation() {    return location;}public void setLocation(String location) {    this.location = location;}public int getGrade() {    return grade;}public void setGrade(int grade) {    this.grade = grade;}@Overridepublic String toString() {    return "Student [flow_id=" + flow_id + ", type=" + type + ", id_card="            + id_card + ", student_name=" + student_name + ", location="            + location + ", grade=" + grade + "]";}

}

package com.curtis.table;

import com.curtis.dao.JdbcDaoImpl;

public class StudentDao extends JdbcDaoImpl<Student> {

}

单元测试类测试各个方法是否愉快
@Test
public void testGet() {
Connection connection = null;
try {
connection = JdbcUtils.getConnection();
String sql = "select flow_id,type,id_card,student_name,location,grade from student where flow_id=?";
Student student=studentDao.getOne(connection, sql, 1001);
System.out.println(student);
} catch (Exception e) {
e.printStackTrace();
} finally{
JdbcUtils.releaseConnection(connection);
}
}