1.目录结构
2.BasicDao.java
static{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (Exception e) {
e.printStackTrace();
}
}
public Connection getConnection() throws SQLException{
String url = "jdbc:mysql://127.0.0.1:3306/dbparam?autoReconnect=true&useUnicode=true&characterEncoding=UTF8";
String user = "root";
String password = "123456";
return DriverManager.getConnection(url, user, password);
}
public void close(ResultSet rs, Statement st, Connection conn){
if(rs!=null){
try {rs.close();} catch (SQLException e) {e.printStackTrace();}
}
if(st!=null){
try {st.close();} catch (SQLException e) {e.printStackTrace();}
}
if(conn!=null){
try {conn.close();} catch (SQLException e) {e.printStackTrace();}
}
}
public String getMethodName(String fieldName){
byte[] buffer = fieldName.getBytes();
buffer[0] = (byte)(buffer[0]-32);
String name = new String(buffer);
return "get"+name;
}
public String setMethodName(String fieldName){
byte[] buffer = fieldName.getBytes();
buffer[0] = (byte)(buffer[0]-32);
String name = new String(buffer);
return "set"+name;
}
3.GetEntity.java
/**
* T为实体对象，可以是由属性和setter/getter组成的实体类，这里要求属性名和查询的数据库字段名相同（顺序可以不一致）
* @author zhzhair
* @param <T>
*/
public class GetEntity<T> extends BasicDao{
/**
* @todo 获取实体对象，T为实体类，sql为sql语句字符串，param为sql中传的参数
* @return T
*/
public T getEntity(Class<T> clazz, String sql, Object[] param) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
Field[] fields = clazz.getDeclaredFields();//实体类（POJO）的属性数组（Declared表示按照顺序）
conn = getConnection();
ps = conn.prepareStatement(sql);
for (int i = 0; i < param.length; i++) {
ps.setObject(i+1, param[i]);
}
rs = ps.executeQuery();
if (rs.next()) {
T entity = clazz.newInstance();//创建实例（给实体类分配内存）
ResultSetMetaData rsmd = rs.getMetaData();//获取数据库表的元数据信息
for (int i = 1; i <= rsmd.getColumnCount(); i++) {
String columnName = rsmd.getColumnName(i);//数据库表的字段名（按照顺序）
for (Field f : fields) {
if (columnName.equalsIgnoreCase(f.getName())) {
Object columnValue = rs.getObject(columnName);//根据属性名获取值
String methodName = setMethodName(f.getName());//实体的属性名首字母必须小写，获取get方法名
Method method = clazz.getMethod(methodName,f.getType());//根据get方法名和属性的类型返回get方法
method.invoke(entity, columnValue);//唤醒get方法（让get方法生效）
}
}
}
return entity;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
close(rs, ps, conn);
}
return null;
}
/**
* @todo 获取实体对象的列表，sql为sql语句字符串，param为sql中传的参数
* @return List<T>
*/
public List<T> getEntityList(Class<T> clazz, String sql, Object[] param) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
List<T> entities = new ArrayList<T>();
try {
Field[] fields = clazz.getDeclaredFields();//bean属性的数组（按照顺序）
conn = getConnection();
ps = conn.prepareStatement(sql);
for (int i = 0; i < param.length; i++) {
ps.setObject(i+1, param[i]);
}
rs = ps.executeQuery();
while (rs.next()) {
T entity = clazz.newInstance();
ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++) {
String columnName = rsmd.getColumnName(i);
for (Field f : fields) {
if (columnName.equalsIgnoreCase(f.getName())) {
Object columnValue = rs.getObject(columnName);
String methodName = setMethodName(f.getName());
Method method = clazz.getMethod(methodName,f.getType());//根据get方法名和属性的类型返回get方法
method.invoke(entity, columnValue);//唤醒get方法（让get方法生效）
}
}
}
entities.add(entity);
}
return entities;
} catch (Exception e) {
e.printStackTrace();
} finally {
close(rs, ps, conn);
}
return null;
}
}