在看了大神们写的代码，人家写的就是又质量，通过看他们的代码，自己也长了一些经验，比如我们在写SQL语句的时候，我们会定义一个变量比如String str = "select * from XXX";这样来写，在代码中，就会有那么长的一句话，看起来很不舒服，然而怎么才能写的代码更加漂亮，看上去第一眼不知道是干什么的，嘿嘿 就是封装起来，就是把一些把一些常用的sql语句封装到一个常量中然后调用这个常量就可以了，如果还有其他的条件的，就在where后面写上一个1=1就可以。
请看代码：
public class SqlConst {
public static final String and = "and";
public static final String select = "select";
public static final String where = "where";
public static final String from = "from";
public static final String order_by = "order by";
public static final String group_by = "group by";
public static final String desc = "desc";
public static final String range = "range";
public static final String range_year = "year";
public static final String range_month = "month";
public static final int function_count = -1;
public static final String OPPORTUNITY_SQL_BEGINNING = "select opportunity from Opportunity opportunity where 1=1 ";
public static final String QUOTATION_SQL_BEGINNING = "select quotation from Quotation quotation where 1=1 ";
public static final String MARKET_SQL_BEGINNING = "select market from Market market where 1=1 ";
public static final String ACTIVITY_SQL_BEGINNING = "select activity from Activity activity where 1=1 ";
public static final String CUSTOMER_SQL_BEGINNING = "select customer from Customer customer where 1=1 ";
public static final String CONTACT_SQL_BEGINNING = "select contact from Contact contact where 1=1 ";
public static final String CLUE_SQL_BEGINNING = "select clue from Clue clue where 1=1 ";
public static final String PRODUCT_SQL_BEGINNING = "select product from Product product where 1=1 ";
public static final String CONTRACT_SQL_BEGINNING = "select contract from Contract contract where 1=1 ";
}
是不是看上去这样写的代码很有水平，在你调用的地方直接类名就可以调用到了，大神们写的代码没有多么难，但是人家写的就是规范，让人看上去，第一眼不知道是干什么的，这就是封装。
同样的下面是对表名称的封装，数据库中有几张表就在一个类中封装几个常量，方便后面的编码。
package com.ebizwindow.crm.constants;
public class TableConst {
public static final String CRM_Customer = "CRM_Customer";
public static final String CRM_Contact = "CRM_Contact";
public static final String CRM_Market = "CRM_Market";
public static final String CRM_Clue = "CRM_Clue";
public static final String CRM_Opportunity = "CRM_Opportunity";
public static final String CRM_Quotation = "CRM_Quotation";
public static final String CRM_Order = "CRM_Order";
public static final String CRM_Activity = "CRM_Activity";
public static final String CRM_Product = "CRM_Product";
public static final String CRM_Contract = "CRM_Contract";
public static final String CRM_PriceBook = "CRM_PriceBook";
public static final String CRM_RPLAN = "CRM_ReceivablesPlan";
public static final String CRM_RRECORD = "CRM_ReceivablesRecord";
public static final String CUSTOMER = "customer";
public static final String CONTACT = "contact";
public static final String MARKET = "market";
public static final String CLUE = "clue";
public static final String QUOTATION = "quotation";
public static final String OPPORTUNITY = "opportunity";
public static final String ORDER = "order_";
public static final String CONTRACT = "contract";
public static final String ACTIVITY = "activity";
public static final String ACTIVITY_HISTORY = "activityHistory";
public static final String PRODUCT = "product";
public static final String PRICEBOOK = "priceBook";
public static final String RPLAN = "receivablesPlan";
public static final String RRECORD = "receivablesRecord";
public static final String REPORT = "report";
public static final String DEPARTMENT = "department";
public static final String OPERATOR = "operator";
public static final String OPERATOR_Operator = "OPERATOR_Operator";
public static final String OPERATOR_Department = "OPERATOR_Department";
}