java学习笔记

1-微软数据库连接

  JDBC下载地址：https://www.microsoft.com/en-us/download/details.aspx?displaylang=en&id=11774

  下载jar包之后可以通过下面的maven命令将jar包安装到自己的私服上。（也可以直接导入架包）

mvn install:install-file -Dfile=sqljdbc4.jar -Dpackaging=jar -DgroupId=com.microsoft.sqlserver -DartifactId=sqljdbc4 -Dversion=4.0

  安装成功之后就可以在pom中引用sqljdbc依赖了。

<dependency>
    <groupId>com.microsoft.sqlserver</groupId>
    <artifactId>sqljdbc4</artifactId>
    <version>4.0</version>
</dependency>

配置文件config.properties

jdbc.driver=com.microsoft.sqlserver.jdbc.SQLServerDriver;
jdbc.url=jdbc:sqlserver://127.0.0.1:1433;DatabaseName=chapter2
jdbc.username=sa
jdbc.password=Passw0rd

2-pom.xml基本配置

    <!-- 统一编码格式 -->
    <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <build>
        <plugins>
            <!-- Compile -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <!-- JDK版本 -->
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

3-数据库访问帮助类

package com.lyra.chapter2.helper;

import com.lyra.chapter2.util.CollectionUtil;
import com.lyra.chapter2.util.PropsUtil;
import org.apache.commons.dbcp2.BasicDataSource;
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.MapListHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * Created by qiyin.gan on 2016/5/18.
 */
public final class DatabaseHelper {
    private static final Logger LOGGER= LoggerFactory.getLogger(DatabaseHelper.class);

    private static final ThreadLocal<Connection> CONNECTION_THREAD_LOCAL;

    private static final QueryRunner QUERY_RUNNER;

    private static final BasicDataSource DATA_SOURCE;

    /*
    private static final String DRIVER;

    private static final String URL;

    private static final String USERNAME;

    private static final String PASSWORD;
*/
    static {
        CONNECTION_THREAD_LOCAL=new ThreadLocal<Connection>();
        QUERY_RUNNER=new QueryRunner();

        Properties config= PropsUtil.loadProps("config.properties");
        /* DRIVER=config.getProperty("jdbc.driver");
        URL=config.getProperty("jdbc.url");
        USERNAME=config.getProperty("jdbc.username");
        PASSWORD=config.getProperty("jdbc.password");
        try{
            Class.forName(DRIVER);
        }
        catch (ClassNotFoundException ex)
        {
            LOGGER.error("can not load jdbc driver",ex);
        }
        */
        String driver=config.getProperty("jdbc.driver");
        String url=config.getProperty("jdbc.url");
        String username=config.getProperty("jdbc.username");
        String password=config.getProperty("jdbc.password");

        DATA_SOURCE=new BasicDataSource();
        DATA_SOURCE.setDriverClassName(driver);
        DATA_SOURCE.setUrl(url);
        DATA_SOURCE.setUsername(username);
        DATA_SOURCE.setPassword(password);

    }

    /**
     * 查询实体列表
     */
    public static <T> List<T> queryEntityList(Class<T> entityClass,Connection connection,String sql,Object... params)
    {
           List<T> entityList;
           try
           {
               entityList=QUERY_RUNNER.query(connection,sql,new BeanListHandler<T>(entityClass),params);
           }
           catch (SQLException ex)
           {
               LOGGER.error("query entity list failure",ex);
               throw new RuntimeException(ex);
           }
           finally {
               //closeConnection(connection);
           }
           return entityList;
    }

    /**
     * 查询实体列表
     */
    public static <T> List<T> queryEntityList(Class<T> entityClass,String sql,Object... params)
    {
        Connection connection=CONNECTION_THREAD_LOCAL.get();
        List<T> entityList;
        try
        {
            entityList=QUERY_RUNNER.query(connection,sql,new BeanListHandler<T>(entityClass),params);
        }
        catch (SQLException ex)
        {
            LOGGER.error("query entity list failure",ex);
            throw new RuntimeException(ex);
        }
        finally {
            //closeConnection();
        }
        return entityList;
    }

    /**
     * 查询实体
     */
    public static <T> T queryEntity(Class<T> entityClass,String sql,Object... params)
    {
        Connection connection=CONNECTION_THREAD_LOCAL.get();
        T entity;
        try
        {
            entity=QUERY_RUNNER.query(connection,sql,new BeanHandler<T>(entityClass),params);
        }
        catch (SQLException ex)
        {
            LOGGER.error("query entity failure",ex);
            throw new RuntimeException(ex);
        }
        finally {
            //closeConnection();
        }
        return entity;
    }


    /**
     * 查询实体列表
     */
    public static List<Map<String,Object>> executeQuery(String sql, Object... params)
    {
        Connection connection=CONNECTION_THREAD_LOCAL.get();
        List<Map<String,Object>> result;
        try
        {
            result=QUERY_RUNNER.query(connection,sql,new MapListHandler(),params);
        }
        catch (SQLException ex)
        {
            LOGGER.error("execute query failure",ex);
            throw new RuntimeException(ex);
        }
        finally {
            //closeConnection();
        }
        return result;
    }

    /**
     * 执行更新语句（包括insert ,update,delete）
     * @param sql
     * @param params
     * @return
     */
    public static int executeUpdate(String sql,Object... params)
    {
         int rows=0;
        try {
            Connection connection=getConnection();
            rows=QUERY_RUNNER.update(connection,sql,params);
        }
        catch (SQLException ex)
        {
            LOGGER.error("execute update failure",ex);
            throw new RuntimeException(ex);
        }
        finally {
            //closeConnection();
        }
        return rows;
    }

    /**
     * 插入实体
     * @param entityClass
     * @param fieldMap
     * @param <T>
     * @return
     */
    public static <T> boolean insertEntity(Class<T> entityClass,Map<String,Object> fieldMap){
        if(CollectionUtil.isEmpty(fieldMap))
        {
            LOGGER.error("can not insert entity: fieldMap is empty");
            return false;
        }
        String sql="INSERT INTO "+getTableName(entityClass);
        StringBuilder columns=new StringBuilder("(");
        StringBuilder values=new StringBuilder("(");
        for(String fieldName :fieldMap.keySet())
        {
            columns.append(fieldName).append(", ");
            values.append("?, ");
        }
        columns.replace(columns.lastIndexOf(", "),columns.length(),")");
        values.replace(columns.lastIndexOf(", "),columns.length(),")");
        sql+=columns+" VALUES "+values;
        Object[] params=fieldMap.values().toArray();
        return executeUpdate(sql,params)==1;
    }

    /**
     * 更新实体
     * @param entityClass
     * @param id
     * @param fieldMap
     * @param <T>
     * @return
     */
    public static <T> boolean updateEntity(Class<T> entityClass,long id,Map<String,Object> fieldMap)
    {
        if(CollectionUtil.isEmpty(fieldMap))
        {
            LOGGER.error("can not update entity: fieldMap is empty");
            return false;
        }
        String sql="UPDATE "+getTableName(entityClass)+" SET ";
        StringBuilder columns=new StringBuilder("(");
        for(String fieldName :fieldMap.keySet())
        {
            columns.append(fieldName).append("=?, ");
        }
        sql+=columns.substring(0,columns.lastIndexOf(", "))+" WHERE id=?";

        List<Object> paramList=new ArrayList<Object>();
        paramList.addAll(fieldMap.values());
        paramList.add(id);
        Object[] params=paramList.toArray();
        return executeUpdate(sql,params)==1;
    }

    /**
     * 删除实体
     * @param entityClass
     * @param id
     * @param <T>
     * @return
     */
    public static <T> boolean deleteEntity(Class<T> entityClass,long id)
    {
        String sql="DELETE FROM "+getTableName(entityClass)+" WHERE id=?";
        return executeUpdate(sql,id)==1;
    }

    private static String getTableName(Class<?> entityClass)
    {
        return entityClass.getSimpleName();
    }

    /**
     * 获取数据库连接
     * @return
     */
    public static Connection getConnection(){
        //原始写法
       /* Connection connection=null;
        try {
            connection= DriverManager.getConnection(URL,USERNAME,PASSWORD);
        }
        catch (SQLException ex)
        {
            LOGGER.error("get conncetion failure",ex);
        }
        return connection;*/
       //线程池写法
        Connection connection=CONNECTION_THREAD_LOCAL.get();
        if(connection==null)
        {
            try {
                //connection= DriverManager.getConnection(URL,USERNAME,PASSWORD);
                connection=DATA_SOURCE.getConnection();
            }
            catch (SQLException ex)
            {
                LOGGER.error("get conncetion failure",ex);
                throw new RuntimeException(ex);
            }
            finally {
                CONNECTION_THREAD_LOCAL.set(connection);
            }
        }
        return connection;
    }

    /**
     * 关闭数据库连接
     * @param connection
     */
    public static void closeConnection(Connection connection)
    {
        if(connection!=null)
        {
            try
            {
                connection.close();
            }
            catch (SQLException ex) {
                LOGGER.error("close connection failure", ex);
            }
        }
    }

    /**
     * 关闭数据库连接
     */
    public static void closeConnection()
    {
        //线程池写法
        Connection connection=CONNECTION_THREAD_LOCAL.get();
        if(connection!=null)
        {
            try
            {
                connection.close();
            }
            catch (SQLException ex) {
                LOGGER.error("close connection failure", ex);
                throw new RuntimeException(ex);
            }
            finally {
                CONNECTION_THREAD_LOCAL.remove();
            }
        }
    }
}