Mybatis 框架总结(四) :dao接口编程

Mybatis 框架总结(二) :增删改查

上一章利用的session的selectList等方法来调用Book.xmld的sql语句，这次在不借助session的情况下来完成增删改查

首先开发一个dao接口，里面有调用方法，不过接口方法的名字要和sql的id一致

package sdibt.lxj.dao;

import java.util.List;
import java.util.Map;

public interface IBookDao {
	
	public void insert1(Map map);
	
	public void delete1(int id);
	
	public void update1(Map map);
	
	public List

Book.xml    namespace必须绑定该dao

Mapper元素只有一个属性namespace，它有两个作用：一是用于区分不同的mapper（在不同的mapper文件里，子元素的id可以相同，mybatis通过namespace和子元素的id联合区分），二是与接口关联（应用程序通过接口访问mybatis时，mybatis通过接口的完整名称查找对应的mapper配置，因此namespace的命名务必小心一定要某接口同名）

  



	
  
     	insert into book(book_name,book_price,book_page) values(#{bookName},#{bookPrice},#{bookPage})
  
  
  
  	delete from book where id=#{id}
  
  
    
    	update book set book_page=#{bookPage} where id=#{id}

	
	
		update book
		
			
				book_name=#{bookName},
			
			
				book_price=#{bookPrice},
				
		
		where id=#{id}		
	
	
	
		select * from book
	
	 
    
    select * from book where id=#{abc}   
      
      
      
    
    	 select * from book where book_page < #{page} and book_name like #{keyword}
      
      
      
      
      	select * from book where id in
      	 
      	 	#{item}
      	 
      
      

测试：

package sdibt.lxj.test;

import java.util.List;
import java.util.Map;
import org.apache.ibatis.session.SqlSession;
import sdibt.lxj.dao.IBookDao;
import sdibt.lxj.util.MybatisUtils;

public class TestMybatis {
	public static void main(String[] args) throws ClassNotFoundException {
		SqlSession session = MybatisUtils.getSession();
		
		IBookDao dao = session.getMapper(IBookDao.class);
		
		List

分析一下是怎么执行sql的

IBookDao dao = session.getMapper(IBookDao.class);            采用动态代理机制获取dao的代理对象       代理模式

既然要创建代理对象，handler切面是不可少了，看一下mybatis的切面，貌似这里只提到了缓存

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    if (Object.class.equals(method.getDeclaringClass())) {
      try {
        return method.invoke(this, args);
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
    }
    final MapperMethod mapperMethod = cachedMapperMethod(method);
    return mapperMethod.execute(sqlSession, args);
  }

既然有了handler，就可以获取代理对象了

获取完代理对象，看看代理对象是怎么执行方法的，肯定要调用切面的invoke方法，接下来会执行方法

 public Object execute(SqlSession sqlSession, Object[] args) {
    Object result;
    if (SqlCommandType.INSERT == command.getType()) {
      Object param = method.convertArgsToSqlCommandParam(args);
      result = rowCountResult(sqlSession.insert(command.getName(), param));
    } else if (SqlCommandType.UPDATE == command.getType()) {
      Object param = method.convertArgsToSqlCommandParam(args);
      result = rowCountResult(sqlSession.update(command.getName(), param));
    } else if (SqlCommandType.DELETE == command.getType()) {
      Object param = method.convertArgsToSqlCommandParam(args);
      result = rowCountResult(sqlSession.delete(command.getName(), param));
    } else if (SqlCommandType.SELECT == command.getType()) {
      if (method.returnsVoid() && method.hasResultHandler()) {
        executeWithResultHandler(sqlSession, args);
        result = null;
      } else if (method.returnsMany()) {
        result = executeForMany(sqlSession, args);
      } else if (method.returnsMap()) {
        result = executeForMap(sqlSession, args);
      } else {
        Object param = method.convertArgsToSqlCommandParam(args);
        result = sqlSession.selectOne(command.getName(), param);
      }
    } else {
      throw new BindingException("Unknown execution method for: " + command.getName());
    }
    if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
      throw new BindingException("Mapper method '" + command.getName() 
          + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
    }
    return result;
  }

现在调用的是select方法

 private  Object executeForMany(SqlSession sqlSession, Object[] args) {
    List result;
    Object param = method.convertArgsToSqlCommandParam(args);
    if (method.hasRowBounds()) {
      RowBounds rowBounds = method.extractRowBounds(args);
      result = sqlSession.selectList(command.getName(), param, rowBounds);
    } else {
      result = sqlSession.selectList(command.getName(), param);
    }
    // issue #510 Collections & arrays support
    if (!method.getReturnType().isAssignableFrom(result.getClass())) {
      if (method.getReturnType().isArray()) {
        return convertToArray(result);
      } else {
        return convertToDeclaredCollection(sqlSession.getConfiguration(), result);
      }
    }
    return result;
  }

这句话，还是调用了xml中的id