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 delete
void 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];
            }
        }
    }
}

@Override
public void batch(Connection connection, String sql, Object[]... args)
        throws SQLException {
    queryRunner.batch(connection, sql, args);
}

@SuppressWarnings("unchecked")
@Override
public <E> E getValue(Connection connection, String sql, Object... args)
        throws SQLException {
    return (E) queryRunner
            .query(connection, sql, new ScalarHandler(), args);
}

@Override
public List<T> getAllList(Connection connection, String sql, Object... args)
        throws SQLException {
    return queryRunner.query(connection, sql, new BeanListHandler<>(clazz),
            args);
}

@Override
public T getOne(Connection connection, String sql, Object... args)
        throws SQLException {
    return queryRunner.query(connection, sql, new BeanHandler<>(clazz),
            args);
}

@Override
public 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;
}

@Override
public 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);
}
}