MyBatis实战篇——实现数据的增删改查

    前面我们已经讲了，MyBatis 是支持普通 SQL 查询，存储过程和高级映射的优秀持久层框架。 MyBatis 消除了几乎所有的 JDBC 代码和参数的手工设置以及对结果集的检索。MyBatis 可以使用简单的XML 或注解用于配置和原始映射，将接口和 Java 的 POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。

    纸上得来终觉浅，理论最终还是要通过实践来验证，今天我们来看下mybatis到底是怎么如何运用到实践中的？

    这里我用到的框架是SSM，所以在这里我们主要解决的是怎么从dao层读取到配置文件再到sql语句，从jsp页面——controller——service这里我们不在提，而从dao层开始。

    dao层：      
<span style="font-family:KaiTi_GB2312;font-size:18px;"> /**
* 导出个人用户
* @param paramMap
* @return
* @throws Exception
*/
public List exportCustomerIndividual(Map paramMap) throws Exception{
return (List) DataAccessor.query(getNameSpace() + ".pageQuery", paramMap, RS_TYPE.LIST);
}
</span>

    然后我们来看看其中的query方法：
     <span style="font-family:KaiTi_GB2312;font-size:18px;"> /**
*
* @param sqlId
* @param paramMap
* @param rsType
* @return
* @throws Exception
*/
public static Object query(final String sqlId, Map paramMap, RS_TYPE rsType) throws SQLException {
Object resultObj = null;
try {
switch (rsType) {
case LIST:
resultObj = sqlMapper.queryForList(sqlId, paramMap);
break;

case MAP:
resultObj = sqlMapper.queryForObject(sqlId, paramMap);
break;

case OBJECT:
resultObj = sqlMapper.queryForObject(sqlId, paramMap);
break;

case PAGED:
DataWrap dw = new DataWrap();
/*
* 增加权限控制
* @author
* @date 2013-10-4
*/
// =========增加权限控制
// 开始=============================================
// 删除此处
// Integer count = (Integer)sqlMapper.queryForObject(sqlId +
// "_count", paramMap);
// dw.recordCount = count.intValue();

int pageSize = -1;
try {
pageSize = Integer.parseInt((String) paramMap.get("__pageSize"));
} catch (Exception e) {
// e.printStackTrace();
pageSize = 20;
}

int currentPage = -1;
try {
currentPage = Integer.parseInt((String) paramMap.get("__currentPage"));
if (currentPage == 0) {
currentPage = 1;
}
} catch (Exception e) {
currentPage = 1;
}

List rslist = sqlMapper.queryForList(sqlId, paramMap);

com.brick.permission.util.ControlPermissionUtil.controlPaginatedList(rslist, paramMap, sqlMapper);

dw.recordCount = rslist.size();

dw.pageCount = dw.recordCount / pageSize + (dw.recordCount % pageSize == 0 ? 0 : 1);
dw.pageSize = pageSize;
dw.currentPage = currentPage;

int startNum = (currentPage - 1) * pageSize;
int endNum = currentPage * pageSize > dw.recordCount ? dw.recordCount : currentPage * pageSize;

List list = new LinkedList();

for (int i = startNum; i < endNum; i++) {
if (i <= rslist.size() - 1) {
list.add(rslist.get(i));
}
}

dw.rs = list;

// =========增加权限控制
// 结束=============================================

resultObj = dw;

}

} catch (SQLException e) {
logger.error("执行查询失败", e);
throw e;
}
return resultObj;
}
</span>   那么我们又是怎么获取spring中的东西呢？
<span style="font-family:KaiTi_GB2312;font-size:18px;">public class DataAccessor {

public static enum RS_TYPE {LIST, MAP, OBJECT, PAGED};
public static enum OPERATION_TYPE {QUERY, INSERT, UPDATE, DELETE};

private static Logger logger = Logger.getLogger(DataAccessor.class);
private static SqlMapClient sqlMapper;

static{

try {
Reader reader = Resources.getResourceAsReader("config/sql/sqlmap_cfg.xml");
sqlMapper = SqlMapClientBuilder.buildSqlMapClient(reader);
reader.close();
} catch (Exception e) {
e.printStackTrace();
// Fail fast.
throw new RuntimeException("Something bad happened while building the SqlMapClient instance." + e, e);
}
}
</span>     首先获得能够连接数据库的配置文件，并且能够告诉我想要实现sql语句在什么地方：

<span style="font-family:KaiTi_GB2312;font-size:18px;"><transactionManager type="JDBC" commitRequired="true">
<dataSource type="SIMPLE">
<property value="oracle.jdbc.driver.OracleDriver" name="JDBC.Driver" />
<!--<property value="jdbc:oracle:thin:@10.172.244.77:1521:oracle" name="JDBC.ConnectionURL" />
<property name="JDBC.Username" value="factoring0002" />
<property name="JDBC.Password" value="HopeDate2014" />-->

<property value="jdbc:oracle:thin:@192.168.0.6:1521:orcl" name="JDBC.ConnectionURL" />
<property value="factoring0813" name="JDBC.Username" />
<property value="1" name="JDBC.Password" />

<property name="Pool.MaximumActiveConnections" value="10" />
<property name="Pool.MaximumIdleConnections" value="5" />
<property name="Pool.MaximumWait" value="500" />
<property name="Pool.TimeToWait" value="500" />

</dataSource>
</transactionManager>

<sqlMap resource="config/sql/map/puhuilicai/customer/CustomerIndividual.xml" />
</span>     最后获得实现的sql语句：
<span style="font-family:KaiTi_GB2312;font-size:18px;"><select id="pageQuery" parameterClass="map" resultClass="java.util.HashMap">
<![CDATA[
SELECT
T1.ID,
T1.CUST_CODE,
NVL(T1.CUST_NAME, T1.USER_NAME) CUST_NAME,
T1.CUST_STATUS,
T1.CUST_TYPE,
T1.USER_NAME,
T1.USER_ID,
T1.MOBILE,
T1.EMAIL,
T1.RESIDENCE_ADDR,
T1.BIRTH,
T7.P_,
FLOOR(TO_NUMBER(SYSDATE-T1.BIRTH)/365) AGE,
T1.SEX,
T1.DOUCUMENT_NUM CUST_NUMBER,
TO_CHAR(T1.CREATE_TIME, 'YYYY-MM-DD HH24:MI:SS') CREATE_TIME,
TO_CHAR(T5.LAST_LOGIN_TIME, 'YYYY-MM-DD HH24:MI:SS') LAST_LOGIN_TIME,
NVL(T2.CERTIFIED_STATUS, 0) PHONE_STATUS,
NVL(T3.CERTIFIED_STATUS, 0) REAL_NAME_STATUS,
NVL(T6.BANK_CARD_STATUS, 1) BANK_CARD_STATUS,
NVL(T4.CERTIFIED_STATUS, 0) EMAIL_STATUS
FROM T_CUST_INDIVIDUAL T1
LEFT JOIN T_AUTH_PHONE T2
ON T1.USER_ID = T2.USER_ID AND T2.CERTIFIED_STATUS = 1
LEFT JOIN T_AUTH_REAL_NAME T3
ON T1.USER_ID = T3.USER_ID AND T3.CERTIFIED_STATUS = 1
LEFT JOIN T_AUTH_EMAIL T4
ON T1.USER_ID = T4.USER_ID AND T4.CERTIFIED_STATUS = 1
LEFT JOIN T_PHONE_ATTRIBUTION T7
ON substr(T1.MOBILE,1,7)=T7.PHONE
LEFT JOIN (SELECT USER_ID, MAX(LOGIN_TIME) LAST_LOGIN_TIME
FROM T_CUST_USER_LOGIN
GROUP BY USER_ID) T5
ON T1.USER_ID = T5.USER_ID
LEFT JOIN T_CUST_BANK T6 ON T1.USER_ID = T6.USER_ID AND T6.STATUS = 0 AND T6.BANK_CARD_STATUS = 2
WHERE T1.STATUS = 0
]]>

<isNotEmpty prepend=" " property="emailStatus" > AND T4.CERTIFIED_STATUS=#emailStatus# </isNotEmpty>
<isNotEmpty prepend=" " property="phoneStatus" > AND T2.CERTIFIED_STATUS=#phoneStatus# </isNotEmpty>
<isNotEmpty prepend=" " property="realNameStatus" > AND T3.CERTIFIED_STATUS=#realNameStatus# </isNotEmpty>
<isNotEmpty prepend=" " property="bankStatus" > AND T6.BANK_CARD_STATUS=#bankStatus# </isNotEmpty>
<isNotEmpty prepend=" " property="start_time" > AND T1.CREATE_TIME >= #start_time# </isNotEmpty>
<isNotEmpty prepend=" " property="end_time" > AND T1.CREATE_TIME <= #end_time# </isNotEmpty>
<isNotEmpty prepend=" " property="selectedPlace" >AND T7.P_ = <![CDATA[$selectedPlace$ ]]> </isNotEmpty>
<isNotEmpty prepend=" " property="searchContent">
<![CDATA[
AND ( T1.CUST_NAME LIKE '%$searchContent$%'
OR T1.USER_NAME LIKE '%$searchContent$%'
OR T1.USER_ID LIKE '%$searchContent$%'
OR T1.EMAIL LIKE '%$searchContent$%'
OR T1.MOBILE LIKE '%$searchContent$%'
OR T1.DOUCUMENT_NUM LIKE '%$searchContent$%')
]]>
</isNotEmpty>

<isEmpty property="ORDERTYPE" >
<![CDATA[ORDER BY T1.CREATE_TIME DESC]]>
</isEmpty>

<isNotEmpty property="ORDERTYPE">
<![CDATA[ORDER BY T1.$ORDERTYPE$]]>
</isNotEmpty>

</select>
</span>    在这里我们可以发现mybatis的灵活之处，我们可以看到里面的isNotEmpty，也就是说如果参数传进来，有这个参数我就执行，没有的话，我就不执行，这样一个sql语句，可以解决很多功能上的问题，用起来很是方便，更大的体现了抽象这一思想。

     很多东西我们只学习理论还是远远不够的，我们还要实践，这样我们才能真正地体会到好处，更好地解决实际问题。