Facade Design Pattern

package com.sheting.design.pattern.demo5;

import java.sql.Connection;

/**
 * @Author SheTing
 * @Time 2018/3/22 8:26
 */
public class MySqlHelper {

    public static Connection getMySqlDBConnection() {
        //get MySql DB connection using connection parameters
        return null;
    }

    public void generateMySqlPDFReport(String tableName, Connection con) {
        //get data from table and generate pdf report
    }

    public void generateMySqlHTMLReport(String tableName, Connection con) {
        //get data from table and generate pdf report
    }

}

package com.sheting.design.pattern.demo5;

import java.sql.Connection;

/**
 * @Author SheTing
 * @Time 2018/3/22 8:26
 */
public class OracleHelper {

    public static Connection getOracleDBConnection(){
        //get Oracle DB connection using connection parameters
        return null;
    }

    public void generateOraclePDFReport(String tableName, Connection con){
        //get data from table and generate pdf report
    }

    public void generateOracleHTMLReport(String tableName, Connection con){
        //get data from table and generate pdf report
    }
}

package com.sheting.design.pattern.demo5;

import java.sql.Connection;

/**
 * @Author SheTing
 * @Time 2018/3/22 8:27
 */
public class HelperFacade {

    public static void generateReport(DBTypes dbType, ReportTypes reportType, String tableName) {
        Connection con = null;
        switch (dbType) {
            case MYSQL:
                con = MySqlHelper.getMySqlDBConnection();
                MySqlHelper mySqlHelper = new MySqlHelper();
                switch (reportType) {
                    case HTML:
                        mySqlHelper.generateMySqlHTMLReport(tableName, con);
                        break;
                    case PDF:
                        mySqlHelper.generateMySqlPDFReport(tableName, con);
                        break;
                }
                break;
            case ORACLE:
                con = OracleHelper.getOracleDBConnection();
                OracleHelper oracleHelper = new OracleHelper();
                switch (reportType) {
                    case HTML:
                        oracleHelper.generateOracleHTMLReport(tableName, con);
                        break;
                    case PDF:
                        oracleHelper.generateOraclePDFReport(tableName, con);
                        break;
                }
                break;
        }

    }

    public static enum DBTypes {
        MYSQL, ORACLE;
    }

    public static enum ReportTypes {
        HTML, PDF;
    }

}

package com.sheting.design.pattern.demo5;

import java.sql.Connection;

/**
 * @Author SheTing
 * @Time 2018/3/22 8:28
 */
public class FacadePatternTest {

    public static void main(String[] args) {
        String tableName = "Employee";

        //generating MySql HTML report and Oracle PDF report without using Facade
        Connection con = MySqlHelper.getMySqlDBConnection();
        MySqlHelper mySqlHelper = new MySqlHelper();
        mySqlHelper.generateMySqlHTMLReport(tableName, con);

        Connection con1 = OracleHelper.getOracleDBConnection();
        OracleHelper oracleHelper = new OracleHelper();
        oracleHelper.generateOraclePDFReport(tableName, con1);

        //generating MySql HTML report and Oracle PDF report using Facade
        HelperFacade.generateReport(HelperFacade.DBTypes.MYSQL, HelperFacade.ReportTypes.HTML, tableName);
        HelperFacade.generateReport(HelperFacade.DBTypes.ORACLE, HelperFacade.ReportTypes.PDF, tableName);
    }

}

门面模式应用

SLF4J，即简单日志门面（Simple Logging Facade for Java），不是具体的日志解决方案，它只服务于各种各样的日志系统。按照官方的说法，SLF4J是一个用于日志系统的简单Facade，允许最终用户在部署其应用时使用其所希望的日志System。