Question

我有从db获取许多记录的问题这是我的主要表格

@DatabaseTable(tableName = "MyTrips")
public class MyTripTable {

@DatabaseField(generatedId = true)
private long id;

@DatabaseField
private long timestamp;


@DatabaseField(foreign = true, foreignAutoRefresh = true )
private ForeignCollection<PortTable> mPorts;

public MyTripTable() {}

public ForeignCollection<PortTable> getPorts() {
    return mPorts;
}

public long getId() {
    return id;
}
}

这是第二个表

@DatabaseTable(tableName = "Ports")
public class PortTable {

@DatabaseField(generatedId = true)
private long id;

@DatabaseField
private long timestamp;

@DatabaseField(foreign = true, foreignAutoRefresh = true )
private MyTripTable myTripTable;

public PortTable() {}
public void setTripAssigned(MyTripTable myTripTable){
    this.myTripTable = myTripTable;
}
}

我需要一个MyTrips有更多Ports 我这样做是example但不起作用

问题在这里：

   private void strawberry(){
    DatabaseHelper helper = OpenHelperManager.getHelper(getApplicationContext(), DatabaseHelper.class);
    RuntimeExceptionDao<MyTripTable, Long> mTrip = helper.getTripRuntimeExcaptionDao();
    RuntimeExceptionDao<PortTable, Long> mPort = helper.getPortRuntimeExcaptionDao();

    long time1 = Calendar.getInstance().getTimeInMillis();

    //crate data
    MyTripTable myFirstTrip = new MyTripTable(153315, "Praha - Gothenburg",       "Big fat woman",
            time1,time1,time1,time1,1,5,6 );
   mTrip.create(myFirstTrip);

    PortTable port1 = new PortTable("Praha",
            "Praha is the capital and largest city of the Czech Republic. ",
            50.078047,
            14.427172);
    port1.setTripAssigned(myFirstTrip);
    PortTable port2 = new PortTable("Praha",
            "Praha is the capital and largest city of the Czech Republic. ",
            50.078047,
            14.427172);
    port2.setTripAssigned(myFirstTrip);
    PortTable port3 = new PortTable("Praha",
            "Praha is the capital and largest city of the Czech Republic. ",
            50.078047,
            14.427172);
    port3.setTripAssigned(myFirstTrip);
    PortTable port4 = new PortTable("Praha",
            "Praha is the capital and largest city of the Czech Republic. ",
            50.078047,
            14.427172);
    port4.setTripAssigned(myFirstTrip);

    mPort.create(port1);
    mPort.create(port2);
    mPort.create(port3);
    mPort.create(port4);


    //Get data
    Log.e("LSA", "----------------------------------TRIPS");
    List<MyTripTable> alltrips = mTrip.queryForAll();
    Log.e("LSA", "TRIPS" + alltrips.toString());
    for (MyTripTable trip : alltrips){
        Log.e("LSA", "Trip: " + trip.toString());
    }

    Log.e("LSA", "----------------------------------PORTS");
    List<PortTable> allPorts = mPort.queryForAll();
    Log.e("LSA", "PORTS" + allPorts.toString());
    for (PortTable port : allPorts){
        Log.e("LSA", "port: " + port.toString());
    }

    Log.e("LSA", "----------------------------------PORTs assigned");

    MyTripTable mOneTrip = mTrip.queryForId(myFirstTrip.getId());
    ForeignCollection<PortTable> mPortsForOneTrip = mOneTrip.getPorts();

    Log.e("LSA", "ports inside trip: " + mPortsForOneTrip);
    }

此部分始终返回null

    ForeignCollection<PortTable> mPortsForOneTrip = mOneTrip.getPorts();

你能帮帮我吗？哪里出错？谢谢你的回复！

Answer 1

基本上，您的主要方法应该是在运行上述代码时给出以下错误。我不知道为什么它一开始就适合你。

Exception in thread "main" java.sql.SQLException: Field 'mPorts' in class interface com.j256.ormlite.dao.ForeignCollection' should use the @ForeignCollectionField annotation not foreign=true

上面的错误在您的类MyTripTable.java中说明，您在集合上标记了@DatabaseField（foreign = true，foreignAutoRefresh = true），而根据文档，您应该使用注释@ForeignCollectionField。我发布了正在运行的代码。

MyTripTable.java的代码

@DatabaseTable(tableName = "MyTrips")
public class MyTripTable {

    @DatabaseField(generatedId = true)
    private long id;

    @DatabaseField
    private long timestamp;

//    @DatabaseField(foreignAutoRefresh = true)
    @ForeignCollectionField(eager = false)
    private ForeignCollection<PortTable> mPorts;

    public MyTripTable() {
    }

    public ForeignCollection<PortTable> getPorts() {
        return mPorts;
    }

    public long getId() {
        return id;
    }

    public long getTimestamp() {
        return timestamp;
    }

    public void setId(long id) {
        this.id = id;
    }

    public void setTimestamp(long timestamp) {
        this.timestamp = timestamp;
    }
}

Port Table.java的代码

@DatabaseTable(tableName = "Ports")
public class PortTable {

    /** The id. */
    @DatabaseField(generatedId = true)
    private long id;

    /** The timestamp. */
    @DatabaseField
    private long timestamp;

    /** The my trip table. */
    @DatabaseField(foreign = true, foreignAutoRefresh = true)
    private MyTripTable myTripTable;

    /**
     * Instantiates a new port table.
     */
    public PortTable() {
    }

    /**
     * Sets the trip assigned.
     *
     * @param myTripTable the new trip assigned
     */
    public void setTripAssigned(MyTripTable myTripTable) {
        this.myTripTable = myTripTable;
    }

    /**
     * Gets the id.
     *
     * @return the id
     */
    public long getId() {
        return id;
    }

    /**
     * Gets the timestamp.
     *
     * @return the timestamp
     */
    public long getTimestamp() {
        return timestamp;
    }

    /**
     * Sets the id.
     *
     * @param id the new id
     */
    public void setId(long id) {
        this.id = id;
    }

    /**
     * Sets the timestamp.
     *
     * @param timestamp the new timestamp
     */
    public void setTimestamp(long timestamp) {
        this.timestamp = timestamp;
    }
}

下面显示了上述代码的执行....

 public static void main(String[] args) throws SQLException {
        String databaseUrl = "jdbc:mysql://localhost:3306/YOUR_DATABASE";

        ConnectionSource connectionSource = new JdbcConnectionSource(databaseUrl, "root", "root");
        // instantiate the dao
        Dao<MyTripTable, Long> tripDao = DaoManager.createDao(connectionSource, MyTripTable.class);
        Dao<PortTable, Long> portDao = DaoManager.createDao(connectionSource, PortTable.class);

        // if you need to create the 'accounts' table make this call
        TableUtils.createTable(connectionSource, MyTripTable.class);
        TableUtils.createTable(connectionSource, PortTable.class);

        long time1 = Calendar.getInstance().getTimeInMillis();

        // crate data
        MyTripTable myFirstTrip = new MyTripTable();
        myFirstTrip.setTimestamp(time1);

        tripDao.create(myFirstTrip);

        PortTable port1 = new PortTable();
        port1.setTimestamp(time1);
        port1.setTripAssigned(myFirstTrip);

        PortTable port2 = new PortTable();
        port2.setTimestamp(time1);
        port2.setTripAssigned(myFirstTrip);

        PortTable port3 = new PortTable();
        port3.setTimestamp(time1);
        port3.setTripAssigned(myFirstTrip);

        portDao.create(port1);
        portDao.create(port2);
        portDao.create(port3);

        List<MyTripTable> alltrips = tripDao.queryForAll();
        for (MyTripTable trip : alltrips) {
            System.out.println(trip);
        }

        List<PortTable> allPorts = portDao.queryForAll();
        for (PortTable port : allPorts) {
            System.out.println(port);
        }

        MyTripTable mOneTrip = tripDao.queryForId(myFirstTrip.getId());
        ForeignCollection<PortTable> mPortsForOneTrip = mOneTrip.getPorts();
        System.out.println(mPortsForOneTrip);

    }

我测试了上面的代码，运行正常。如果您有任何进一步的问题，请告诉我。

我无法从表中获取值。关系一对多

1 个答案: