ronment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
//4. 将创建的Envronment对象设置到configuration 对象中
configuration.setEnvironment(environmentBuilder.build());
}
}
}
}
private boolean isSpecifiedEnvironment(String id)
{
if (environment == null)
{
throw new BuilderException("No environment specified.");
}
else if (id == null)
{
throw new BuilderException("Environment requires an id attribute.");
}
else if (environment.equals(id))
{
return true;
}
return false;
}
(4)返回Configuration对象:
将上述的MyBatis初始化基本过程的序列图细化:
基于XML配置创建Configuration对象的过程
7.3 基于Java API手动加载XML配置文件创建Configuration对象,并使用SqlSessionFactory对象##
我们可以使用XMLConfigBuilder手动解析XML配置文件来创建Configuration对象,代码如下:
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
// 手动创建XMLConfigBuilder,并解析创建Configuration对象
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, null,null);
Configuration configuration=parse();
// 使用Configuration对象创建SqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
// 使用MyBatis
SqlSession sqlSession = sqlSessionFactory.openSession();
List list = sqlSession.selectList("com.foo.bean.BlogMapper.queryAllBlogInfo");
7.4 涉及到的设计模式##
初始化的过程涉及到创建各种对象,所以会使用一些创建型的设计模式。在初始化的过程中,Builder模式运用的比较多。
7.4.1 Builder模式应用1: SqlSessionFactory的创建###
对于创建SqlSessionFactory时,会根据情况提供不同的参数,其参数组合可以有以下几种:
根据情况提供不同的参数,创建SqlSessionFactory
由于构造时参数不定,可以为其创建一个构造器Builder,将SqlSessionFactory的构建过程和表示分开:
MyBatis将SqlSessionFactoryBuilder和SqlSessionFactory相互独立
7.4.2 Builder模式应用2: 数据库连接环境Environment对象的创建###
在构建Configuration对象的过程中,XMLConfigBuilder解析 mybatis XML配置文件节点
节点时,会有以下相应的代码:
private void environmentsElement(XNode context) throws Exception {
if (context != null) {
if (environment == null) {
environment = context.getStringAttribute("default");
}
for (XNode child : context.getChildren()) {
String id = child.getStringAttribute("id");
//是和默认的环境相同时,解析之
if (isSpecifiedEnvironment(id)) {
TransactionFactory txFactory = transactionManagerElement(child.eva lNode("transactionManager"));
DataSourceFactory dsFactory = dataSourceElement(child.eva lNode("dataSource"));
DataSource dataSource = dsFactory.getDataSource();
//使用了Environment内置的构造器Builder,传递id 事务工厂和数据源
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
configuration.setEnvironment(environmentBuilder.build());
}
}
}
}
在Environment内部,定义了静态内部Builder类:
public final class Environment {
private final String id;
private final TransactionFactory transactionFactory;
private final DataSource dataSource;
public Environment(String id, TransactionFactory transactionFactory, DataSource dataSource) {
if (id == null) {
throw new IllegalArgumentException("Parameter 'id' must not be null");
}
if (transactionFactory == null) {
throw new IllegalArgumentException("Parameter 'transactionFactory' must not be null");
}
this.id = id;
if (dataSource == null) {
throw new IllegalArgumentException("