基於JDBC封裝的BaseDao(實例代碼)。本站提示廣大學習愛好者：（基於JDBC封裝的BaseDao(實例代碼)）文章只能為提供參考，不一定能成為您想要的結果。以下是基於JDBC封裝的BaseDao(實例代碼)正文
比來空閒時萌生寫一寫dao的封裝的例子，就將之前寫的整頓一下。
public class BaseDao<T> {
Connection conn;
PreparedStatement st;
ResultSet rs;
JdbcUtil jdbcUtil = new JdbcUtil();
int result = 0;
private Class<T> persistentClass;
@SuppressWarnings("unchecked")
public BaseDaoUtil(){
conn = jdbcUtil.getConnection();
ParameterizedType type = (ParameterizedType) getClass().getGenericSuperclass();
persistentClass = (Class<T>) type.getActualTypeArguments()[0];
}
/**
* 保留
* @param entity
* @return
*/
public int save(T entity) throws Exception{
String sql = "INSERT INTO "+ entity.getClass().getSimpleName().toLowerCase() +" (";
List<Method> list = this.matchPojoMethods(entity,"get");
Iterator<Method> iter = list.iterator();
Object obj[] = new Object[list.size()];
int i = 0;
//拼接字段次序 insert into table name(id,name,email,
while(iter.hasNext()) {
Method method = iter.next();
sql += method.getName().substring(3).toLowerCase() + ",";
if (method.getReturnType().getSimpleName().indexOf("Date") !=-1) {
SimpleDateFormat sbf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
obj[i] = sbf.format(method.invoke(entity, new Object[]{}));
}else {
obj[i] = method.invoke(entity, new Object[]{});
}
i++;
}
//去失落最初一個,符號insert insert into table name(id,name,email) values(
sql = sql.substring(0, sql.lastIndexOf(",")) + ") values(";
//拼裝預編譯SQL語句insert insert into table name(id,name,email) values(?,?,?,
for(int j = 0; j < list.size(); j++) {
sql += "?,";
}
//去失落SQL語句最初一個,符號insert insert into table name(id,name,email) values(?,?,?);
sql = sql.substring(0, sql.lastIndexOf(",")) + ")";
//到此SQL語句拼接完成,打印SQL語句
System.out.println(sql);
try {
st = conn.prepareStatement(sql);
for (int j = 0; j < obj.length; j++) {
st.setObject(j+1, obj[j]);
}
result = st.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
jdbcUtil.getClose(rs, st, conn);
return result;
}
/**
* 刪除
* @param object
* @return
* @throws SQLException
*/
public int deleteId(Object object) throws Exception{
String sql = "delete from "+ persistentClass.getSimpleName().toLowerCase() +" where ";
//經由過程子類的結構函數,取得參數化類型的詳細類型.好比BaseDAO<T>也就是取得T的詳細類型
T entity = persistentClass.newInstance();
//寄存Pojo(或被操作表)主鍵的辦法對象
Method idMethod = null;
List<Method> list = this.matchPojoMethods(entity, "set");
Iterator<Method> iter = list.iterator();
//過濾獲得Method對象
while(iter.hasNext()) {
Method tempMethod = iter.next();
if(tempMethod.getName().indexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
idMethod = tempMethod;
} else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))){
idMethod = tempMethod;
}
}
//第一個字母轉為小寫
sql += idMethod.getName().substring(3,4).toLowerCase()+idMethod.getName().substring(4) + " = ?";
System.out.println(sql);
st = conn.prepareStatement(sql);
//斷定id的類型
if(object instanceof Integer) {
st.setInt(1, (Integer)object);
} else if(object instanceof String){
st.setString(1, (String)object);
}
result = st.executeUpdate();
jdbcUtil.getClose(rs, st, conn);
return result;
}
/**
* 修正
* @param entity
* @return
* @throws Exception
*/
public int update(T entity) throws Exception{
String sql = "update "+ entity.getClass().getSimpleName().toLowerCase() +" set ";
List<Method> list = this.matchPojoMethods(entity, "get");
//裝載參數
Object obj[] = new Object[list.size()];
int i = 0;
//暫時Method對象,擔任迭代古裝method對象.
Method tempMethod = null;
//因為修正時不須要修正ID,所以按次序加參數則應當把Id移到最初.
Method idMethod = null;
Iterator<Method> iter = list.iterator();
while(iter.hasNext()) {
tempMethod = iter.next();
//假如辦法名中帶有ID字符串而且長度為2,則視為ID.
if(tempMethod.getName().lastIndexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
obj[list.size()-1] = tempMethod.invoke(entity, new Object[]{});
//把ID字段的對象寄存到一個變量中,然後在聚集中刪失落.
idMethod = tempMethod;
iter.remove();
//假如辦法名去失落set/get字符串今後與pojo + "id"想相符(年夜小寫不敏感),則視為ID
} else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))) {
obj[list.size()-1] = tempMethod.invoke(entity, new Object[]{});
idMethod = tempMethod;
iter.remove();
}
}
//把迭代指針移到第一名
iter = list.iterator();
while(iter.hasNext()) {
tempMethod = iter.next();
sql += tempMethod.getName().substring(3).toLowerCase() + "= ?,";
obj[i] = tempMethod.invoke(entity, new Object[]{});
i++;
}
//去失落最初一個,符號
sql = sql.substring(0,sql.lastIndexOf(","));
//添加前提
sql += " where " + idMethod.getName().substring(3).toLowerCase() + " = ?";
//SQL拼接完成,打印SQL語句
System.out.println(sql);
st = conn.prepareStatement(sql);
for (int j = 0; j < obj.length; j++) {
st.setObject(j+1, obj[j]);
}
result = st.executeUpdate();
jdbcUtil.getClose(rs, st, conn);
return result;
}
public T findById(Object object) throws Exception{
String sql = "select * from "+ persistentClass.getSimpleName().toLowerCase() +" where ";
//經由過程子類的結構函數,取得參數化類型的詳細類型.好比BaseDAO<T>也就是取得T的詳細類型
T entity = persistentClass.newInstance();
//寄存Pojo(或被操作表)主鍵的辦法對象
Method idMethod = null;
List<Method> list = this.matchPojoMethods(entity, "set");
Iterator<Method> iter = list.iterator();
//過濾獲得Method對象
while(iter.hasNext()) {
Method tempMethod = iter.next();
if(tempMethod.getName().indexOf("Id") != -1 && tempMethod.getName().substring(3).length() == 2) {
idMethod = tempMethod;
} else if((entity.getClass().getSimpleName() + "Id").equalsIgnoreCase(tempMethod.getName().substring(3))){
idMethod = tempMethod;
}
}
//第一個字母轉為小寫
sql += idMethod.getName().substring(3,4).toLowerCase()+idMethod.getName().substring(4) + " = ?";
System.out.println(sql);
st = conn.prepareStatement(sql);
//斷定id的類型
if(object instanceof Integer) {
st.setInt(1, (Integer)object);
} else if(object instanceof String){
st.setString(1, (String)object);
}
rs = st.executeQuery();
//把指針指向迭代器第一行
iter = list.iterator();
//封裝
while(rs.next()) {
while(iter.hasNext()) {
Method method = iter.next();
if(method.getParameterTypes()[0].getSimpleName().indexOf("String") != -1) {
//因為list聚集中,method對象掏出的辦法次序與數據庫字段次序紛歧致(好比:list的第一個辦法是setDate,而數據庫按次序取的是"123"值)
//所以數據庫字段采取名字對應的方法取.
this.setString(method, entity, rs.getString(method.getName().substring(3).toLowerCase()));
} else if(method.getParameterTypes()[0].getSimpleName().indexOf("Date") != -1){
this.setDate(method, entity, rs.getDate(method.getName().substring(3).toLowerCase()));
}else {
this.setInt(method, entity, rs.getInt(method.getName().substring(3).toLowerCase()));
}
}
}
jdbcUtil.getClose(rs, st, conn);
return entity;
}
/**
* 過濾以後Pojo類一切帶傳入字符串的Method對象,前往List聚集.
*/
private List<Method> matchPojoMethods(T entity,String methodName) {
//取得以後Pojo一切辦法對象
Method[] methods = entity.getClass().getDeclaredMethods();
//List容器寄存一切帶get字符串的Method對象
List<Method> list = new ArrayList<Method>();
//過濾以後Pojo類一切帶get字符串的Method對象,存入List容器
for(int index = 0; index < methods.length; index++) {
if(methods[index].getName().indexOf(methodName) != -1) {
list.add(methods[index]);
}
}
return list;
}
/**
* 參數類型為String時,為entity字段設置參數,對應set
*/
public String setString(Method method, T entity, String arg) throws Exception{
return (String)method.invoke(entity, new Object[]{arg});
}
/**
* 參數類型為Date時,為entity字段設置參數,對應set
*/
public Date setDate(Method method, T entity, Date arg) throws Exception{
return (Date)method.invoke(entity, new Object[]{arg});
}
/**
* 參數類型為Integer或int時,為entity字段設置參數,對應set
*/
public Integer setInt(Method method, T entity, Integer arg) throws Exception{
return (Integer)method.invoke(entity, new Object[]{arg});
}
}
以上這篇基於JDBC封裝的BaseDao(實例代碼)就是小編分享給年夜家的全體內容了，願望能給年夜家一個參考，也願望年夜家多多支撐。
