XUtils下載地址 http://www.oschina.net/p/xutils

以下是對demo的分析

進入DbFragment

首先看到的是

 DbManager.DaoConfig daoConfig = new DbManager.DaoConfig()
            .setDbName("test")
            .setDbDir(new File("/sdcard")) // "sdcard"的寫法並非最佳實踐, 這裡為了簡單, 先這樣寫了.
            .setDbVersion(2)
            .setDbUpgradeListener(new DbManager.DbUpgradeListener() {
                @Override
                public void onUpgrade(DbManager db, int oldVersion, int newVersion) {
                    // TODO: ...
                    // db.addColumn(...);
                    // db.dropTable(...);
                    // ...
                }
            });
 

此程式碼大致寫了關於資料庫名稱、版本、路徑以及更新操作

所以可以進入 new DbManager.DaoConfig() 中去檢視具體資訊

<pre name="code" class="java">public interface DbManager extends Closeable 

資料庫介面訪問 此介面定義了關於資料增、刪、查、改、版本相關操作

DbManager中的內部類定義了相關資料庫配置、更新資訊

  public static class DaoConfig {
        private File dbDir;
        private String dbName = "xUtils.db"; // default db name
        private int dbVersion = 1;
        private boolean allowTransaction = true;
        private DbUpgradeListener dbUpgradeListener;
        private TableCreateListener tableCreateListener;
 

此處注意物件的==與equals的不同

DaoConfig包含如下程式碼

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            DaoConfig daoConfig = (DaoConfig) o;

            if (!dbName.equals(daoConfig.dbName)) return false;
            return dbDir == null ? daoConfig.dbDir == null : dbDir.equals(daoConfig.dbDir);
        }

        @Override
        public int hashCode() {
            int result = dbName.hashCode();
            result = 31 * result + (dbDir != null ? dbDir.hashCode() : 0);
            return result;
        }
 

介面分析大致結束

然後回到DbFragment檢視資料庫具體操作

   private void onTestDbClick(View view) {

        // 一對多: (本示例的程式碼)
        // 自己在多的一方(child)儲存另一方的(parentId), 查詢的時候用parentId查parent或child.
        // 一對一:
        // 在任何一邊儲存另一邊的Id並加上唯一屬性: @Column(name = "parentId", property = "UNIQUE")
        // 多對多:
        // 再建一個關聯表, 儲存兩邊的id. 查詢分兩步: 先查關聯表得到id, 再查對應表的屬性.

        String temp = "";

        try {

            DbManager db = x.getDb(daoConfig);

此處真正的呼叫了資料庫然後進入org.xutils.x;去檢視具體實現

/**
 * Created by wyouflf on 15/6/10.
 * 任務控制中心, http, image, db, view注入等介面的入口.
 * 需要在在application的onCreate中初始化: x.Ext.init(this);
 */
public final class x {

    private x() {
    }

此處可以看出是所有模組的封裝類

   public static DbManager getDb(DbManager.DaoConfig daoConfig) {
        return DbManagerImpl.getInstance(daoConfig);
    }

此處可以看到DbManagerImpl類

public final class DbManagerImpl implements DbManager {

    //*************************************** create instance ****************************************************

    /**
     * key: dbName
     */
    private static HashMap<DaoConfig, DbManagerImpl> daoMap = new HashMap<DaoConfig, DbManagerImpl>();

    private SQLiteDatabase database;
    private DaoConfig daoConfig;
    private boolean allowTransaction;

    private DbManagerImpl(DaoConfig config) {
        if (config == null) {
            throw new IllegalArgumentException("daoConfig may not be null");
        }
        this.database = createDatabase(config);
        this.daoConfig = config;
        this.allowTransaction = config.isAllowTransaction();
    }

    public synchronized static DbManager getInstance(DaoConfig daoConfig) {

        if (daoConfig == null) {//使用預設配置
            daoConfig = new DaoConfig();
        }

        DbManagerImpl dao = daoMap.get(daoConfig);
        if (dao == null) {
            dao = new DbManagerImpl(daoConfig);
            daoMap.put(daoConfig, dao);
        } else {
            dao.daoConfig = daoConfig;
        }

        // update the database if needed
        SQLiteDatabase database = dao.database;
        int oldVersion = database.getVersion();
        int newVersion = daoConfig.getDbVersion();
        if (oldVersion != newVersion) {
            if (oldVersion != 0) {
                DbUpgradeListener upgradeListener = daoConfig.getDbUpgradeListener();
                if (upgradeListener != null) {
                    upgradeListener.onUpgrade(dao, oldVersion, newVersion);
                } else {
                    try {
                        dao.dropDb();
                    } catch (DbException e) {
                        LogUtil.e(e.getMessage(), e);
                    }
                }
            }
            database.setVersion(newVersion);
        }

        return dao;
    }

注意public final class DbManagerImpl 為final 並且private DbManagerImpl(DaoConfig config) 私有建構函式

上述程式碼建立了database 並儲存到HashMap<DaoConfig, DbManagerImpl> daoMap = new HashMap<DaoConfig, DbManagerImpl>();

建立database程式碼

 private SQLiteDatabase createDatabase(DaoConfig config) {
        SQLiteDatabase result = null;

        File dbDir = config.getDbDir();
        if (dbDir != null && (dbDir.exists() || dbDir.mkdirs())) {
            File dbFile = new File(dbDir, config.getDbName());
            result = SQLiteDatabase.openOrCreateDatabase(dbFile, null);
        } else {
            result = x.app().openOrCreateDatabase(config.getDbName(), 0, null);
        }
        return result;
    }

如果資料庫路徑不存在那麼使用預設路徑並但會database

返回DbFragment繼續往下走

看到關於資料庫表的操作

  Parent test = db.selector(Parent.class).where("id", "in", new int[]{1, 3, 6}).findFirst();

關於

public final class Selector<T> 與  public class WhereBuilder  
db.selector(Parent.class).where("id", "in", new int[]{1, 3, 6})  產生sql語句

</pre>此處程式碼是為了封裝sql資料<p>一下是具體分析</p><p></p><pre name="code" class="java"> @Override
    public <T> Selector<T> selector(Class<T> entityType) throws DbException {
        return Selector.from(TableEntity.get(this, entityType));
    }

public final class TableEntity<T> {

    private final DbManager db;
    private final String name;
    private final String onCreated;
    private ColumnEntity id;
    private Class<T> entityType;
    private Constructor<T> constructor;

    /**
     * key: columnName
     */
    private final LinkedHashMap<String, ColumnEntity> columnMap;

    /**
     * key: dbName#className
     */
    private static final HashMap<String, TableEntity<?>> tableMap = new HashMap<String, TableEntity<?>>();

tableEntity對錶結構和是否存在實現封裝

public class WhereBuilder

對sql語句的封裝

最後執行findFirst

    public T findFirst() throws DbException {
        if (!table.tableIsExist()) return null;

        this.limit(1);
        Cursor cursor = table.getDb().execQuery(this.toString());
        if (cursor != null) {
            try {
                if (cursor.moveToNext()) {
                    return CursorUtils.getEntity(table, cursor);
                }
            } catch (Throwable e) {
                throw new DbException(e);
            } finally {
                IOUtil.closeQuietly(cursor);
            }
        }
        return null;
    }

到此第一個操作語句結束

接著往下看進入第二個與資料庫操作有關的方法

db.save(parent);

進入DbManagerImpl實現程式碼

  @Override
    public void save(Object entity) throws DbException {
        try {
            beginTransaction();

            if (entity instanceof List) {
                List<?> entities = (List<?>) entity;
                if (entities.isEmpty()) return;
                TableEntity<?> table = TableEntity.get(this, entities.get(0).getClass());
                createTableIfNotExist(table);
                for (Object item : entities) {
                    execNonQuery(SqlInfoBuilder.buildInsertSqlInfo(table, item));
                }
            } else {
                TableEntity<?> table = TableEntity.get(this, entity.getClass());
                createTableIfNotExist(table);
                execNonQuery(SqlInfoBuilder.buildInsertSqlInfo(table, entity));
            }

            setTransactionSuccessful();
        } finally {
            endTransaction();
        }
    }

此方法首先開啟了事務，然後判斷傳入的物件是否是集合再進行資料操作、此處運用了instanceof去判斷是否是集合

此方法中呼叫了createTableIfNotExist(table)和execNonQuery(SqlInfoBuilder.buildInsertSqlInfo(table, entity))首先判斷表是否存在然後進行資料庫操作

關於異常的處理程式中直接向外層丟擲未做處理

其他方法的呼叫流程大體相似故不再分析

此部落格中進行了大致呼叫流程分析未對具體進行描述

關於程式碼的具體實現請下載原始碼進行檢視