android項目里面很多都會有使用sqlite來保存數據。原生api真心不好使啊，要寫超多超多的代碼，還要寫顧慮很多細節問題。于是乎就想偷懶了，干脆去網上找個orm框架吧！
Ok，google it。篩選一下，就鎖定了ormlite和greendao。簡單看了一下，ormlite簡單好用，比較符合JavaEE開發者使用習慣，注解真的很好用啊！再去greendao官網逛逛，他說我們的目標是：
最牛掰的性能
超好用的API
為Android大大優化
最小的內存使用
******
再翻翻看，還有同ormlite的性能對比：
上面可以看到，greeendao的insert和update效率要比ormlite快兩倍左右，load更是夸張到4倍多。尼瑪也太厲害了吧，優化這么狠。這么一大堆好處，還不趕緊使使。
我們可以在官網上直接下來，也可去github項目主頁上下載源碼。建議去下載github哈，因為有源碼有列子，比較直觀易懂。源碼使用gradle構建，需要安裝gradle插件。其實真正也只有依賴一個freemaker.jar，直接網上下載一個就好。下面新建一個java工程，注意是java工程不是android工程。導入freemaker.jar和greendao-generator.jar，加入到build path。建一個如下的類：
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56publicclassDaoGenerator {
publicstaticvoidmain(String[] args)throwsException {
// first parameter for version, second for default generate package
Schema schema =newSchema(1,"com.xckevin.example.model");
addNote(schema);
addCustomerOrder(schema);
addUser(schema);
// set dao class generate package
schema.setDefaultJavaPackageDao("com.xckevin.example.dao");
// keep custom code block
schema.enableKeepSectionsByDefault();
newDaoGenerator().generateAll(schema,"../GreenDaoExample/src");
}
privatestaticvoidaddNote(Schema schema) {
Entity note = schema.addEntity("Note");
note.addIdProperty();
note.addStringProperty("text").notNull();
note.addStringProperty("comment");
note.addDateProperty("date");
}
privatestaticvoidaddUser(Schema schema) {
Entity user = schema.addEntity("User");
user.setTableName("t_user");
user.addIdProperty();
user.addStringProperty("account").unique();
user.addStringProperty("password");
user.addDateProperty("birthday");
user.addShortProperty("gender");
user.addIntProperty("height");
user.addFloatProperty("weight");
user.addDateProperty("registerTime");
user.implementsInterface("Jsonable");
}
privatestaticvoidaddCustomerOrder(Schema schema) {
Entity customer = schema.addEntity("Customer");
customer.addIdProperty();
customer.addStringProperty("name").notNull();
Entity order = schema.addEntity("Order");
order.setTableName("ORDERS");// "ORDER" is a reserved keyword
order.addIdProperty();
Property orderDate = order.addDateProperty("date").getProperty();
Property customerId = order.addLongProperty("customerId").notNull().getProperty();
order.addToOne(customer, customerId);
ToMany customerToOrders = customer.addToMany(order, customerId);
customerToOrders.setName("orders");
customerToOrders.orderAsc(orderDate);
}
}
代碼號簡單的話，看名字就知道是什么意思了。greendao支持各種類型的哇，還支持一對一、一對多、多對多的關系，很強悍！直接運行，代碼生成
自動生成model和dao，倍兒爽！隨便看一個model類：
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123packagecom.xckevin.example.model;
// THIS CODE IS GENERATED BY greenDAO, EDIT ONLY INSIDE THE "KEEP"-SECTIONS
// KEEP INCLUDES - put your custom includes here
importorg.json.JSONException;
importorg.json.JSONObject;
// KEEP INCLUDES END
/**
* Entity mapped to table t_user.
*/
publicclassUserimplementsJsonable {
privateLong id;
privateString account;
privateString password;
privatejava.util.Date birthday;
privateShort gender;
privateInteger height;
privateFloat weight;
privatejava.util.Date registerTime;
// KEEP FIELDS - put your custom fields here
// KEEP FIELDS END
publicUser() {
}
publicUser(Long id) {
this.id = id;
}
publicUser(Long id, String account, String password, java.util.Date birthday, Short gender, Integer height, Float weight, java.util.Date registerTime) {
this.id = id;
this.account = account;
this.password = password;
this.birthday = birthday;
this.gender = gender;
this.height = height;
this.weight = weight;
this.registerTime = registerTime;
}
publicLong getId() {
returnid;
}
publicvoidsetId(Long id) {
this.id = id;
}
publicString getAccount() {
returnaccount;
}
publicvoidsetAccount(String account) {
this.account = account;
}
publicString getPassword() {
returnpassword;
}
publicvoidsetPassword(String password) {
this.password = password;
}
publicjava.util.Date getBirthday() {
returnbirthday;
}
publicvoidsetBirthday(java.util.Date birthday) {
this.birthday = birthday;
}
publicShort getGender() {
returngender;
}
publicvoidsetGender(Short gender) {
this.gender = gender;
}
publicInteger getHeight() {
returnheight;
}
publicvoidsetHeight(Integer height) {
this.height = height;
}
publicFloat getWeight() {
returnweight;
}
publicvoidsetWeight(Float weight) {
this.weight = weight;
}
publicjava.util.Date getRegisterTime() {
returnregisterTime;
}
publicvoidsetRegisterTime(java.util.Date registerTime) {
this.registerTime = registerTime;
}
// KEEP METHODS - put your custom methods here
@Override
publicUser parse(JSONObject jsonObj) {
// TODO Auto-generated method stub
try{
id = jsonObj.getLong("id");
account = jsonObj.getString("account");
returnthis;
}catch(JSONException e) {
e.printStackTrace();
}
returnnull;
}
// KEEP METHODS END
}
注意上面的// KEEP代碼塊中是手動加入了，當設置了
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schema.enableKeepSectionsByDefault
后，該部分代碼塊在下次更新的時候會保留下來。
dao類中也有各種基本的方法，如insert,update,delete等等。基本可能完成大部分需求了，終于不用寫那么繁瑣的數據庫操作啦！
再看看怎么在client獲取到dao，注意client要加入greendao.jar哦。有了dao就可以對數據庫各種操作了！
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5DevOpenHelper helper =newDaoMaster.DevOpenHelper(this,"notes-db",null);
db = helper.getWritableDatabase();
daoMaster =newDaoMaster(db);
daoSession = daoMaster.newSession();
userDao = daoSession.getUserDao();
總體來說，ormlite使用簡單，學習成本低，容易上手，效率比greendao偏慢一點。greendao耦合性高，使用時要另外使用一個java工程創建，開始環境搭建比較麻煩，但是一旦上手還是十分容易使用的，并且效率最好。個人還是推薦使用greendao。
