ORM 对象关系型数据库

用法（点我）

1. 添加依赖

    // In your root build.gradle file:
    buildscript {
        repositories {
            jcenter()
            mavenCentral() // add repository
        }
        dependencies {
            classpath 'com.android.tools.build:gradle:3.1.1'
            classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // add plugin
        }
    }

    //可以把以下部分放在module中
    // In your app projects build.gradle file:
    apply plugin: 'org.greenrobot.greendao' // apply plugin

    dependencies {
        implementation 'org.greenrobot:greendao:3.2.2' // add library
    }

2. 配置greendao（在添加依赖的module中）

    android {
        ...
    }

    greendao {
        //当前版本
        schemaVersion 1
        // set package of generated classes
        daoPackage "com.curry.db.dao"
        //自动生成的代码存储的路径，默认是 build/generated/source/greendao.
        targetGenDir 'src/main/java'
        //true的时候自动生成测试单元
        generateTests false
        //测试单元的生成目录默认是 src / androidTest / java
        //targetGenDirTests:
    }

3. 构建实体类

    @Entity(
            // If you have more than one schema, you can tell greenDAO
            // to which schema an entity belongs (pick any string as a name).
    //        schema = "myschema",//不常用

            // Flag to make an entity "active": Active entities have update,
            // delete, and refresh methods.
            active = true,//不常用--会自动生成更新、删除、刷新的代码

            // Specifies the name of the table in the database.
            // By default, the name is based on the entities class name.
            nameInDb = "AWESOME_USERS",//声明了该表数据库中的表名

            // Define indexes spanning multiple columns here.
            indexes = {
                    @Index(value = "name DESC", unique = true)
            },

            // Flag if the DAO should create the database table (default is true).
            // Set this to false, if you have multiple entities mapping to one table,
            // or the table creation is done outside of greenDAO.
            createInDb = true,//不常用

            // Whether an all properties constructor should be generated.
            // A no-args constructor is always required.
            generateConstructors = true,//不常用

            // Whether getters and setters for properties should be generated if missing.
            generateGettersSetters = true//不常用
    )
    public class User {
        @Id(autoincrement = true)
        private Long id; //推荐使用long型

        @Index(unique = true)
        private String index;//指定自己的索引；并表示唯一
    //    @Unique String index;

        @Property(nameInDb = "USERNAME")
        private String name;

        @NotNull
        private int repos;

        @Transient//表示不存储在数据库中
        private int tempUsageCount; // not persisted

4. 执行make project

会在daoPackage对应配置的目录中自动生成3个文件：DaoMaster、DaoSession、[实体类名]Dao;
如果在@Entity注解中配置了active = true，会自动生成升级、删除、刷新的方法