模拟Mybatis的实现方法

2023-09-25 03:24:06 287

所需要用到的其他工具或技术:

项目管理工具:Maven

测试运行工具:Junit

数据库 :Derby

XML操作工具:Dom4j

继续不废话

MavenDependencies:


junit
junit
4.9
test


org.apache.derby
derby
10.10.2.0


org.apache.derby
derbyclient
10.10.2.0


dom4j
dom4j
1.6.1

SQL建表及数据插入（如果在第一节中作过，可以跳过此步）:

CREATETABLEUSER_TEST_TB(
IDINTPRIMARYKEY,
USERNAMEVARCHAR(20)NOTNULL,
PASSWORDVARCHAR(20)NOTNULL,
NICKNAMEVARCHAR(20)NOTNULL
);
INSERTINTOUSER_TEST_TBVALUES(1,'1st','111','Jack');
INSERTINTOUSER_TEST_TBVALUES(2,'2nd','222','Rose');
INSERTINTOUSER_TEST_TBVALUES(3,'3rd','333','Will');

Mybatis配置文件src/main/resource源目录下

test-mybatis-configuration.xml

User.java对象类(src/main/java/com/bjpowernode/practice目录下)

packagecom.bjpowernode.practice;
/**
*
*UserModel
*
*/
publicclassUser
{
privateStringid;
privateStringusername;
privateStringpassword;
privateStringnickname;
publicStringgetId()
{
returnid;
}
publicvoidsetId(Stringid)
{
this.id=id;
}
publicStringgetUsername()
{
returnusername;
}
publicvoidsetUsername(Stringusername)
{
this.username=username;
}
publicStringgetPassword()
{
returnpassword;
}
publicvoidsetPassword(Stringpassword)
{
this.password=password;
}
publicStringgetNickname()
{
returnnickname;
}
publicvoidsetNickname(Stringnickname)
{
this.nickname=nickname;
}
}

Select.java注解类（src/main/java/com/bjpowernode/practice/annotation目录下）

packagecom.bjpowernode.practice.annotation;
importjava.lang.annotation.ElementType;
importjava.lang.annotation.Retention;
importjava.lang.annotation.RetentionPolicy;
importjava.lang.annotation.Target;
/**标注此注解只能用在方法上*/
@Target(ElementType.METHOD)
/**标注此注解生命周期是在Runtime运行时*/
@Retention(RetentionPolicy.RUNTIME)
public@interfaceSelect
{
Stringvalue();
}

UserMapper.java基于Annotation的配置类（src/main/java/com/bjpowernode/practice/annotation目录下）

packagecom.bjpowernode.practice.annotation;
importcom.bjpowernode.practice.User;
importjava.util.List;
publicinterfaceUserMapper
{
@Select("select*fromUSER_TEST_TB")
publicListgetUser();
}

Mapper.java对象类（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
/**
*
*存储查询结果对象
*
*/
publicclassMapper
{
/**
*返回类型
*/
privateStringresultType;
/**
*查询ＳＱＬ
*/
privateStringquerySql;
publicStringgetResultType()
{
returnresultType;
}
publicvoidsetResultType(StringresultType)
{
this.resultType=resultType;
}
publicStringgetQuerySql()
{
returnquerySql;
}
publicvoidsetQuerySql(StringquerySql)
{
this.querySql=querySql;
}
}

SQLSelectProxy.javaAOP动态代理类（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
importcom.bjpowernode.practice.annotation.Select;
importjava.lang.reflect.InvocationHandler;
importjava.lang.reflect.Method;
importjava.sql.PreparedStatement;
importjava.sql.ResultSet;
importjava.util.List;
publicclassSQLSelectProxyimplementsInvocationHandler
{
@Override
publicObjectinvoke(Objectproxy,Methodmethod,Object[]args)throwsThrowable
{
/**
*获得Mapper方法上的Select注解,以此来取得注解中的SQL语句
*/
Selectselect=method.getAnnotation(Select.class);
if(!method.isAnnotationPresent(Select.class))
{
thrownewRuntimeException("缺少@Select注解!");
}
PreparedStatementpstmt=null;
ResultSetrs=null;
Objectobj=null;
try
{
pstmt=SqlSessionImpl.connection.prepareStatement(select.value());
rs=pstmt.executeQuery();
/**
*获得Method的返回对象类型,此处应当作判断处理,当List的时候,当只返回一个对象的时候.
*为了简单实现功能并与第一节中测试文件不发生冲突起见,此处当作List处理
*/
StringreturnType=method.getGenericReturnType().toString();//java.util.List
if(returnType.startsWith(List.class.getName()))
{
//去掉我们不需要的字符串，得到List中的类型
returnType=returnType.replace(List.class.getName(),"").replace("<","").replace(">","");
}
else
{
//返回其他对象应当作其他处理，此处为了简单起见，暂不处理
}
obj=SqlSessionImpl.executeQuery(rs,returnType);
}
finally
{
if(rs!=null&&!rs.isClosed())
{
rs.close();
}
if(pstmt!=null&&!pstmt.isClosed())
{
pstmt.close();
}
}
returnobj;
}
}

SqlSession.javaMybatis模拟接口（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
importjava.util.List;
/**
*
*模拟SqlSession
*
*/
publicinterfaceSqlSession
{
publicTgetMapper(Classclazz);
publicListselectList(Stringquery)throwsException;
}

SqlSessionFactory.javaMybatis模拟类（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
importjava.io.IOException;
importjava.io.InputStream;
importjava.util.HashMap;
importjava.util.List;
importjava.util.Map;
importorg.dom4j.Document;
importorg.dom4j.DocumentException;
importorg.dom4j.Element;
importorg.dom4j.io.SAXReader;
/**
*
*模拟SqlSessionFactory
*
*/
publicclassSqlSessionFactory
{
privateInputStreamconfiguration;
publicSqlSessionopenSession()throwsIOException
{
SqlSessionImplsession=newSqlSessionImpl();
loadConfigurations(session);
returnsession;
}
/**
*
*通过Ｄｏｍ４ｊ读取配置文件信息
*
*@paramsession
*@throwsIOException
*/
privatevoidloadConfigurations(finalSqlSessionImplsession)throwsIOException
{
try
{
Documentdocument=newSAXReader().read(configuration);
Elementroot=document.getRootElement();
Listmappers=root.element("mappers").elements("mapper");
for(Elementmapper:mappers)
{
if(mapper.attribute("resource")!=null)
{
session.setXmlSQLs(loadXMLConfiguration(mapper.attribute("resource").getText()));
}
if(mapper.attribute("class")!=null)
{
}
}
}
catch(Exceptione)
{
System.out.println("读取配置文件错误!");
}
finally
{
configuration.close();
}
}
/**
*
*通过ｄｏｍ４ｊ读取Ｍａｐｐｅｒ．ｘｍｌ中的信息
*
*@paramresource
*@return
*@throwsDocumentException
*@throwsIOException
*/
privateMaploadXMLConfiguration(Stringresource)throwsDocumentException,IOException
{
Mapmap=newHashMap();
InputStreamis=null;
try
{
is=this.getClass().getClassLoader().getResourceAsStream(resource);
Documentdocument=newSAXReader().read(is);
Elementroot=document.getRootElement();
if(root.getName().equalsIgnoreCase("mapper"))
{
Stringnamespace=root.attribute("namespace").getText();
for(Elementselect:(List)root.elements("select"))
{
MappermapperModel=newMapper();
mapperModel.setResultType(select.attribute("resultType").getText());
mapperModel.setQuerySql(select.getText().trim());
map.put(namespace+"."+select.attribute("id").getText(),mapperModel);
}
}
}
finally
{
is.close();
}
returnmap;
}
publicInputStreamgetConfiguration()
{
returnconfiguration;
}
publicvoidsetConfiguration(InputStreamconfiguration)
{
this.configuration=configuration;
}
}

SqlSessionFactoryBuilder.javaMybatis模拟类（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
importjava.io.InputStream;
/**
*
*模拟SqlSessionFactoryBuilder
*
*/
publicclassSqlSessionFactoryBuilder
{
publicSqlSessionFactorybuild(InputStreamis)
{
SqlSessionFactorysessionFactory=newSqlSessionFactory();
sessionFactory.setConfiguration(is);
returnsessionFactory;
}
}

SqlSessionImpl.javaMybatis模拟类（src/main/java/com/bjpowernode/practice/simulation目录下）

packagecom.bjpowernode.practice.simulation;
importjava.lang.reflect.Method;
importjava.lang.reflect.Proxy;
importjava.sql.Connection;
importjava.sql.DriverManager;
importjava.sql.PreparedStatement;
importjava.sql.ResultSet;
importjava.util.ArrayList;
importjava.util.List;
importjava.util.Map;
/**
*
*模拟SqlSessionImpl
*
*/
publicclassSqlSessionImplimplementsSqlSession
{
/**DBconnection*/
publicstaticConnectionconnection;
privateMapxmlSQLs;
privateListannotationClasses;
publicSqlSessionImpl()
{
/**
*driverString和connString应该是从配置文件读取，这里简化了
*/
finalStringdriverString="org.apache.derby.jdbc.ClientDriver";
finalStringconnString="jdbc:derby://localhost:1527/bjpowernode;create=true";
try
{
Class.forName(driverString);
/**获得DB连接*/
connection=DriverManager.getConnection(connString);
}
catch(Exceptione)
{
System.out.println("获取DBConnection出错！");
}
}
/**
*基于Annotation的数据库操作
*
*/
@Override
publicTgetMapper(Classclazz)
{
TclazzImpl=
(T)Proxy.newProxyInstance(this.getClass().getClassLoader(),newClass[]{clazz},newSQLSelectProxy());
returnclazzImpl;
}
/**
*
*基于XML的查询操作
*/
@Override
publicListselectList(Stringquery)throwsException
{
PreparedStatementpstmt=null;
ResultSetrs=null;
try
{
/**简单的PreparedStatemeJDBC实现*/
pstmt=connection.prepareStatement(xmlSQLs.get(query).getQuerySql());
rs=pstmt.executeQuery();
/**执行查询操作*/
returnexecuteQuery(rs,xmlSQLs.get(query).getResultType());
}
finally
{
if(!rs.isClosed())
{
rs.close();
}
if(!pstmt.isClosed())
{
pstmt.close();
}
}
}
/**
*
*执行查询操作，并将查询到的结果与配置中的ResultType根据变量名一一对应，通过反射调用Set方法注入各个变量的值
*
*@paramrs
*@paramtype
*@return
*@throwsException
*/
publicstaticListexecuteQuery(ResultSetrs,Stringtype)throwsException
{
intcount=rs.getMetaData().getColumnCount();
ListcolumnNames=newArrayList();
for(inti=1;i<=count;i++)
{
columnNames.add(rs.getMetaData().getColumnName(i));
}
finalListlist=newArrayList

模拟Mybatis的实现方法

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