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

Maven Dependencies:

<dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.9</version> <scope>test</scope> </dependency> <dependency> <groupId>org.apache.derby</groupId> <artifactId>derby</artifactId> <version>10.10.2.0</version> </dependency> <dependency> <groupId>org.apache.derby</groupId> <artifactId>derbyclient</artifactId> <version>10.10.2.0</version> </dependency> <dependency> <groupId>dom4j</groupId> <artifactId>dom4j</artifactId> <version>1.6.1</version> </dependency>

SQL 建表及数据插入（如果在第一节中作过，可以跳过此步）:

CREATE TABLE USER_TEST_TB( ID INT PRIMARY KEY, USERNAME VARCHAR(20) NOT NULL, PASSWORD VARCHAR(20) NOT NULL, NICKNAME VARCHAR(20) NOT NULL ); INSERT INTO USER_TEST_TB VALUES(1,'1st','111','Jack'); INSERT INTO USER_TEST_TB VALUES(2,'2nd','222','Rose'); INSERT INTO USER_TEST_TB VALUES(3,'3rd','333','Will');

Mybatis配置文件 src/main/resource源目录下

test-mybatis-configuration.xml<?xml version="1.0" encoding="UTF-8" ?> <configuration> <properties> <property name="driver" value="org.apache.derby.jdbc.ClientDriver" /> <property name="url" value="jdbc:derby://localhost:1527/bjpowernode;create=true" /> </properties> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="${driver}" /> <property name="url" value="${url}" /> </dataSource> </environment> </environments> <mappers> <mapper class="com.bjpowernode.practice.annotation.UserMapper" /> <mapper resource="com/bjpowernode/practice/xml/UserMapper.xml" /> </mappers> </configuration>

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

package com.bjpowernode.practice; /** * * User Model * */ public class User { private String id; private String username; private String password; private String nickname; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; } }

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

package com.bjpowernode.practice.annotation; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.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 @interface Select { String value(); }

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

package com.bjpowernode.practice.annotation; import com.bjpowernode.practice.User; import java.util.List; public interface UserMapper { @Select("select * from USER_TEST_TB") public List<User> getUser(); }

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

package com.bjpowernode.practice.simulation; /** * * 存储查询结果对象 * */ public class Mapper { /** * 返回类型 */ private String resultType; /** * 查询ＳＱＬ */ private String querySql; public String getResultType() { return resultType; } public void setResultType(String resultType) { this.resultType = resultType; } public String getQuerySql() { return querySql; } public void setQuerySql(String querySql) { this.querySql = querySql; } }

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

package com.bjpowernode.practice.simulation; import com.bjpowernode.practice.annotation.Select; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.List; public class SQLSelectProxy implements InvocationHandler { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { /** * 获得Mapper方法上的Select注解,以此来取得注解中的SQL语句 */ Select select = method.getAnnotation(Select.class); if (!method.isAnnotationPresent(Select.class)) { throw new RuntimeException("缺少@Select注解!"); } PreparedStatement pstmt = null; ResultSet rs = null; Object obj = 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 */ String returnType = method.getGenericReturnType().toString();//java.util.List<com.bjpowernode.practice.User> 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(); } } return obj; } }

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

package com.bjpowernode.practice.simulation; import java.util.List; /** * * 模拟SqlSession * */ public interface SqlSession { public <T> T getMapper(Class<T> clazz); public <E> List<E> selectList(String query) throws Exception; }

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

package com.bjpowernode.practice.simulation; import java.io.IOException; import java.io.InputStream; import java.util.HashMap; import java.util.List; import java.util.Map; import org.dom4j.Document; import org.dom4j.DocumentException; import org.dom4j.Element; import org.dom4j.io.SAXReader; /** * * 模拟SqlSessionFactory * */ public class SqlSessionFactory { private InputStream configuration; public SqlSession openSession() throws IOException { SqlSessionImpl session = new SqlSessionImpl(); loadConfigurations(session); return session; } /** * * 通过Ｄｏｍ４ｊ读取配置文件信息 * * @param session * @throws IOException */ private void loadConfigurations(final SqlSessionImpl session) throws IOException { try { Document document = new SAXReader().read(configuration); Element root = document.getRootElement(); List<Element> mappers = root.element("mappers").elements("mapper"); for (Element mapper : mappers) { if (mapper.attribute("resource") != null) { session.setXmlSQLs(loadXMLConfiguration(mapper.attribute("resource").getText())); } if (mapper.attribute("class") != null) { } } } catch (Exception e) { 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 * * @param resource * @return * @throws DocumentException * @throws IOException */ private Map<String, Mapper> loadXMLConfiguration(String resource) throws DocumentException, IOException { Map<String, Mapper> map = new HashMap<String, Mapper>(); InputStream is = null; try { is = this.getClass().getClassLoader().getResourceAsStream(resource); Document document = new SAXReader().read(is); Element root = document.getRootElement(); if (root.getName().equalsIgnoreCase("mapper")) { String namespace = root.attribute("namespace").getText(); for (Element select : (List<Element>) root.elements("select")) { Mapper mapperModel = new Mapper(); mapperModel.setResultType(select.attribute("resultType").getText()); mapperModel.setQuerySql(select.getText().trim()); map.put(namespace + "." + select.attribute("id").getText(), mapperModel); } } } finally { is.close(); } return map; } public InputStream getConfiguration() { return configuration; } public void setConfiguration(InputStream configuration) { this.configuration = configuration; } }

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

package com.bjpowernode.practice.simulation; import java.io.InputStream; /** * * 模拟SqlSessionFactoryBuilder * */ public class SqlSessionFactoryBuilder { public SqlSessionFactory build(InputStream is) { SqlSessionFactory sessionFactory = new SqlSessionFactory(); sessionFactory.setConfiguration(is); return sessionFactory; } }

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

package com.bjpowernode.practice.simulation; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import java.util.Map; /** * * 模拟SqlSessionImpl * */ public class SqlSessionImpl implements SqlSession { /** DB connection */ public static Connection connection; private Map<String, Mapper> xmlSQLs; private List<String> annotationClasses; public SqlSessionImpl() { /** * driverString 和 connString 应该是从配置文件读取，这里简化了 */ final String driverString = "org.apache.derby.jdbc.ClientDriver"; final String connString = "jdbc:derby://localhost:1527/bjpowernode;create=true"; try { Class.forName(driverString); /** 获得DB连接 */ connection = DriverManager.getConnection(connString); } catch (Exception e) { System.out.println("获取DBConnection出错！"); } } /** * 基于Annotation的数据库操作 * */ @Override public <T> T getMapper(Class<T> clazz) { T clazzImpl = (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[] {clazz}, new SQLSelectProxy()); return clazzImpl; } /** * * 基于XML的查询操作 */ @Override public <E> List<E> selectList(String query) throws Exception { PreparedStatement pstmt = null; ResultSet rs = null; try { /** 简单的PreparedStateme JDBC实现 */ pstmt = connection.prepareStatement(xmlSQLs.get(query).getQuerySql()); rs = pstmt.executeQuery(); /** 执行查询操作 */ return executeQuery(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 * * @param rs * @param type * @return * @throws Exception */ public static <E> List<E> executeQuery(ResultSet rs, String type) throws Exception { int count = rs.getMetaData().getColumnCount(); List<String> columnNames = new ArrayList<String>(); for (int i = 1; i <= count; i++) { columnNames.add(rs.getMetaData().getColumnName(i)); } final List list = new ArrayList<Object>(); while (rs.next()) { Class modelClazz = Class.forName(type); Object obj = modelClazz.newInstance(); for (Method setMethods : modelClazz.getMethods()) { for (String columnName : columnNames) { if (setMethods.getName().equalsIgnoreCase("set" + columnName)) { setMethods.invoke(obj, rs.getString(columnName)); } } } list.add(obj); } return list; } public Map<String, Mapper> getXmlSQLs() { return xmlSQLs; } public void setXmlSQLs(Map<String, Mapper> xmlSQLs) { this.xmlSQLs = xmlSQLs; } public List<String> getAnnotationClasses() { return annotationClasses; } public void setAnnotationClasses(List<String> annotationClasses) { this.annotationClasses = annotationClasses; } }

UserMapper.xml 基于XML的Mapper配置文件（src/main/java/com/bjpowernode/practice/xml目录下）

<?xml version="1.0" encoding="UTF-8" ?> <!-- namespace 当基于XML进行配置的时候是根据namespace+id来拼接进行SQL操作 --> <mapper namespace="com.bjpowernode.practice.UserMapper"> <!-- select 查询 --> <select id="getUser" resultType="com.bjpowernode.practice.User"> select * from USER_TEST_TB </select> </mapper>

TestMyBatis.java 测试类(src/test/java/com/bjpowernode/practice目录下)

package com.bjpowernode.practice; import com.bjpowernode.practice.annotation.UserMapper; import com.bjpowernode.practice.simulation.SqlSession; import com.bjpowernode.practice.simulation.SqlSessionFactory; import com.bjpowernode.practice.simulation.SqlSessionFactoryBuilder; import com.bjpowernode.practice.simulation.SqlSessionImpl; import java.io.InputStream; import java.sql.SQLException; import java.text.MessageFormat; import java.util.List; import org.junit.After; import org.junit.Before; import org.junit.Test; public class TestMyBatis { /** 配置置文件 */ private String source; private InputStream inputStream; private SqlSessionFactory sqlSessionFactory; @Before public void setUp() { source = "test-mybatis-configuration.xml"; } /** * * 基于XML格式配置的测试方法 * */ @Test public void testXMLConfingure() { try { /** * 获得Session */ inputStream = TestMyBatis.class.getClassLoader().getResourceAsStream(source); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSession session = sqlSessionFactory.openSession(); /** * 执行Ｑｕｅｒｙ操作 */ List<User> users = (List) session.selectList("com.bjpowernode.practice.UserMapper.getUser"); System.out.println("Query by XML configuration..."); /** * 打印结果 */ this.printUsers(users); } catch (Exception e) { e.printStackTrace(); } } /** * * 基于Annotation配置的测试方法 * */ @Test public void testAnnotationConfingure() { try { inputStream = TestMyBatis.class.getClassLoader().getResourceAsStream(source); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSession session = sqlSessionFactory.openSession(); UserMapper userMapper = session.getMapper(UserMapper.class); System.out.println("\r\nQuery by annotation configuration..."); this.printUsers(userMapper.getUser()); } catch (Exception e) { e.printStackTrace(); } } @After public void clearUp() throws SQLException { if (SqlSessionImpl.connection != null && !SqlSessionImpl.connection.isClosed()) { SqlSessionImpl.connection.close(); } } private void printUsers(final List<User> users) { int count = 0; for (User user : users) { System.out.println(MessageFormat.format("==User[{0}]=================", ++count)); System.out.println("User Id: " + user.getId()); System.out.println("User UserName: " + user.getUsername()); System.out.println("User Password: " + user.getPassword()); System.out.println("User nickname: " + user.getNickname()); } } }

以上就是基于XML以及Annotation的方式对Mybatis实现了一个简单的模拟。旨在理解Mybatis的工作原理。

笔者一直觉得当学习一个工具类技术的时候，路线应该是

1.实现一个小例子

2.找材料理解其中原理

3.学习技术细节，并动手全部实现

4.在全部学完之后动手做一个小项目，尽可能的使用这个在技术中的各个环节。

总结

以上所述是小编给大家介绍的模拟Mybatis的实现方法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！