[TOC]
特别说明：以下代码来源网上，来源地址已经丢失。
入口类
public class APP {
public static void main(String[] args){
MySqlSession sqlSession = new MySqlSession();
// jdk代理
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = mapper.getUserById("1");
System.out.println(" user: "+user);
}
}
jdk代理
MySqlSession.java
public class MySqlSession {
private Excutor excutor = new MyExcutor();
private MyConfiguration myConfiguration = new MyConfiguration();
public <T> T selectOne(String sql, Object parameter)
{
return excutor.query(sql,parameter);
}
public <T> T getMapper(Class<T> clas){
return (T)Proxy.
newProxyInstance(clas.getClassLoader(),
new Class[]{clas},
new MyMapperProxy(this,myConfiguration));
}
}
MyMapperProxy.java
public class MyMapperProxy implements InvocationHandler{
private MySqlSession mySqlSession;
private MyConfiguration myConfiguration;
public MyMapperProxy(MySqlSession mySqlSession, MyConfiguration myConfiguration) {
this.mySqlSession = mySqlSession;
this.myConfiguration = myConfiguration;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
// 解析xml文档，封装到MapperBean对象中
MapperBean mapperBean = myConfiguration.readMapper();
// 判断这个接口类的路径和xml的nameSpace是否一致
if (!method.getDeclaringClass().getName().equals(mapperBean.getInterfaceName()))
{
return null;
}
List<Function> list = mapperBean.getList();
if (list != null && list.size() > 0)
{
for (Function function : list)
{
// 这里就进行判断接口类里面的方法的名称和xml配置文件里面的id是否一致
if (method.getName().equals(function.getFuncName()))
{
// 实际执行的sql语句
return mySqlSession.selectOne(function.getSql(),String.valueOf(args[0]));
}
}
}
return null;
}
}
数据库连接
MyConfiguration.java
处理数据库连接和xml配置文件的对象化封装。
public class MyConfiguration {
private static String driver = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://127.0.0.1:3306/sys?useUnicode=true&characterEncoding=utf-8&useSSL=false";
private static String username = "root";
private static String password = "123456";
// 用于管理数据库连接池，ThreadLocal能够实现当前线程的操作都是用同一个Connection，保证了事务！
private static ThreadLocal<Connection> connContainer = new ThreadLocal<Connection>();
/**
* 获取数据库连接
* @return
*/
public Connection getConnection() throws Exception{
Connection conn = connContainer.get();
Class.forName(driver);
conn = DriverManager.getConnection(url,username,password);
conn.setAutoCommit(false);
return conn;
}
/***
* 关闭链接
*/
public void closeConnection() throws Exception
{
Connection conn = connContainer.get();
if (conn != null)
{
conn.close();
}
connContainer.remove();
}
/***
* 读取写入SQL的配置文件，获取他的SQL语句，返回值，传入的参数
* @param path
* @return
*/
public MapperBean readMapper()
{
ClassLoader loader = ClassLoader.getSystemClassLoader();
MapperBean mapperBean = new MapperBean();
try {
InputStream stream = MyConfiguration.class.getResourceAsStream("/maizi/UserMapper.xml");
SAXReader reader = new SAXReader();
Document document = reader.read(stream);
Element root = document.getRootElement();
// 把nameSpace值为接口名
mapperBean.setInterfaceName(root.attributeValue("nameSpace").trim());
// 存储方法
List<Function> list = new ArrayList<Function>();
// 遍历根节点下面所有节点
for(Iterator rootIter = root.elementIterator();rootIter.hasNext();)
{
Function fun = new Function();
Element e = (Element) rootIter.next();
String sqltype = e.getName().trim();
String funcName = e.attributeValue("id").trim();
String sql = e.getText().trim();
String resultType = e.attributeValue("resultType").trim();
// sql 类型是 查询还是修改等
fun.setSqlType(sqltype);
fun.setFuncName(funcName);
Object newInstance = null;
// 在这里直接实例化返回的对象
newInstance = Class.forName(resultType).newInstance();
fun.setResultType(newInstance);
fun.setSql(sql);
System.out.println(" fun: "+fun.toString());
list.add(fun);
}
mapperBean.setList(list);
}catch (Exception e){
e.printStackTrace();
}
return mapperBean;
}
}
配置文件处理
UserMapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<mapper nameSpace="mapper.UserMapper">
<select id="getUserById" resultType ="mapper.User">
select * from user where id = ?
</select>
</mapper>
MapperBean.java
@Data
public class MapperBean {
private String interfaceName; // 接口名
private List<Function> list; // 接口下所有方法
}
Function.java
@Data
@ToString
public class Function {
private String sqlType;
private String funcName;
private String sql;
private Object resultType;
private String parameterType;
}
User.java
@Data
@ToString
public class User {
private String id;
private String userName;
private String passWord;
}
接口类
UserMapper.java
public interface UserMapper {
public User getUserById(String id);
}
实际执行sql语句类
MyExcutor.java
public class MyExcutor implements Excutor{
private MyConfiguration myConfiguration = new MyConfiguration();
@Override
public <T> T query(String sql, Object parameter) {
try {
Connection connection = myConfiguration.getConnection();
ResultSet set = null;
PreparedStatement pre = null;
pre = connection.prepareStatement(sql);
pre.setString(1,parameter.toString());
set = pre.executeQuery();
User u = new User();
while (set.next())
{
u.setId(set.getString(1));
u.setUserName(set.getString(2));
u.setPassWord(set.getString(3));
}
return (T)u;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
总结
解析xml配置文件
<?xml version="1.0" encoding="UTF-8"?>
<mapper nameSpace="mapper.UserMapper">
<select id="getUserById" resultType ="mapper.User">
select * from user where id = ?
</select>
</mapper>
获取里面的nameSpace，然后根据前面的jdk代理传入的
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
为了就是找到xml配置文件的id和接口的方法对应，
User user = mapper.getUserById("1");
然后在代理类里面进行实际的sql的操作和返回数据和对象的填充。
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