jPetStore 源码分析

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jPetStore 源码分析

jPetStore 作为ibatis的一个成功实例，此刻我们就来分析下它的结构
下面这个类是dao的初始化类，开始的静态块负责把数据库建立
...

public class DaoConfig {

  private static final String resource = "com/ibatis/jpetstore/persistence/dao.xml";
  private static final DaoManager daoManager;

  static {
    try {
      daoManager = newDaoManager(null);
      Properties props = Resources.getResourceAsProperties("properties/database.properties");
      String url = props.getProperty("url");
      String driver = props.getProperty("driver");
      String username = props.getProperty("username");
      String password = props.getProperty("password");
      if (url.equals("jdbc:hsqldb:mem:jpetstore")) {
        Class.forName(driver).newInstance();
        Connection conn = DriverManager.getConnection(url, username, password);
        try {
          ScriptRunner runner = new ScriptRunner(conn, false, false);
          runner.setErrorLogWriter(null);
          runner.setLogWriter(null);
          runner.runScript(Resources.getResourceAsReader("ddl/hsql/jpetstore-hsqldb-schema.sql"));
          runner.runScript(Resources.getResourceAsReader("ddl/hsql/jpetstore-hsqldb-dataload.sql"));
        } finally {
          conn.close();
        }
      }
    } catch (Exception e) {
      throw new RuntimeException("Description.  Cause: " + e, e);
    }

  }

  public static DaoManager getDaoManager() {
    return daoManager;
  }

  public static DaoManager newDaoManager(Properties props) {
    try {
      Reader reader = Resources.getResourceAsReader(resource);
      return DaoManagerBuilder.buildDaoManager(reader, props);
    } catch (Exception e) {
      throw new RuntimeException("Could not initialize DaoConfig.  Cause: " + e, e);
    }
  }

}

静态方法newDaoManager是读取dao.xml中的配置创建DaoManagerBuilder对象实例
在service层通过类似如下的语句来生产数据操作对象：
DaoManager daoMgr = DaoConfig.getDaoManager();
this.accountDao = (AccountDao) daoMgr.getDao(AccountDao.class);
AccountDao是一个数据库操作接口
这些类包括在ibatis-dao-2.jar中
在dao层通过调用template包中的一些类如：
queryForObject("getAccountByUsernameAndPassword", account);
其中getAccountByUsernameAndPassword是映射文件中配置的sql的名称，account是
配置中规定的查询条件封装类实例
下面我们来看看配置文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE daoConfig

PUBLIC "-//ibatis.apache.org//DTD DAO Configuration 2.0//EN"

"http://ibatis.apache.org/dtd/dao-2.dtd">

<property name="SqlMapConfigResource"

value="com/ibatis/jpetstore/persistence/sqlmapdao/sql/sql-map-config.xml"/>

</transactionManager>

<dao interface="com.ibatis.jpetstore.persistence.iface.ItemDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.ItemSqlMapDao"/>

<dao interface="com.ibatis.jpetstore.persistence.iface.SequenceDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.SequenceSqlMapDao"/>

<dao interface="com.ibatis.jpetstore.persistence.iface.AccountDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.AccountSqlMapDao"/>

<dao interface="com.ibatis.jpetstore.persistence.iface.CategoryDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.CategorySqlMapDao"/>

<dao interface="com.ibatis.jpetstore.persistence.iface.ProductDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.ProductSqlMapDao"/>

<dao interface="com.ibatis.jpetstore.persistence.iface.OrderDao"

implementation="com.ibatis.jpetstore.persistence.sqlmapdao.OrderSqlMapDao"/>

</context>

</daoConfig>

这是dao.xml。它在初始化DaoManagerBuilder时被调用

...

<property name="SqlMapConfigResource"

value="com/ibatis/jpetstore/persistence/sqlmapdao/sql/sql-map-config.xml"/>

</transactionManager>

...

引用了sql-map-config.xml配置文件
其他的配置项是对dao接口以及实现类的描述
现在我们把视线跳转到ibatis的sql-map-config.xml配置上来

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE sqlMapConfig PUBLIC "-//ibatis.apache.org//DTD SQL Map Config 2.0//EN"

"http://ibatis.apache.org/dtd/sql-map-config-2.dtd">

</dataSource>

</transactionManager>

</sqlMapConfig>

在<transactionManager type="JDBC">配置项中配置采用通过传统JDBC commit/rollback实现事务支持
dataSource中配置的是所用的连接池类型
SIMPLE是ibatis内置的dataSource实现，其中实现了一个简单的
数据库连接池机制，对应ibatis 实现类为
com.ibatis.sqlmap.engine.datasource.SimpleDataSourceFactory。
sqlMap节点是配置具体dao的映射引用
以下是Account类的sql映射配置片段

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"

"http://ibatis.apache.org/dtd/sql-map-2.dtd">

...

UPDATE ACCOUNT SET

EMAIL = #email#,

FIRSTNAME = #firstName#,

LASTNAME = #lastName#,

STATUS = #status#,

ADDR1 = #address1#,

ADDR2 = #address2:VARCHAR#,

CITY = #city#,

STATE = #state#,

ZIP = #zip#,

COUNTRY = #country#,

PHONE = #phone#

WHERE USERID = #username#

</update>

...

再#之间内容与pojo类的属性对应
由于ibatis采用的是“半自动化”的ORM机制，所以具体的sql语句需要自己编写。这样
sql的优化也是自己来完成的。这样对sql性能要求较高的系统是个好消息。