Nullpointer exception while connecting to DB using MyBatis

Question

I am having the following issue: when I am connecting to db using MyBatis I get an NPE.

Here is the class for setting connection:

public class SetDBConnection {

    private Mapper mapper;
    private SqlSession session;
    private Configuration configuration;

    public SetDBConnection() {


        configuration = new Configuration();
        configuration.setJdbcTypeForNull(JdbcType.VARCHAR);
        configuration.setLogImpl(Slf4jImpl.class);
        configuration.setDefaultExecutorType(ExecutorType.REUSE);
        configuration.addMapper(Mapper.class);

        Properties properties = null;
        try {
            properties = readProperties();
        } catch (IOException e) {
            e.printStackTrace();
        }
        configuration.setVariables(properties);

    }


    public Mapper openSession() {

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
        session = sqlSessionFactory.openSession();

        mapper = session.getMapper(Mapper.class);
        return mapper;
    }

    public void closeSession() {
        session.commit();
        session.close();
    }

    private Properties readProperties() throws IOException {
        Properties properties = new Properties();
        InputStream inputStream = getClass().getClassLoader()
                .getResourceAsStream("connection.properties");


        if (inputStream != null) {
            properties.load(inputStream);
        } else {
            throw new FileNotFoundException("property file  not found in the classpath");
        }
        inputStream.close();

        return properties;
    }
}

And here I call it and try to Insert data SetDBConnection conn = new SetDBConnection();

    Person p = new Person();
    p.setName("Alex");
    p.setLastName("Bondar");
    p.setTelephone("+79267157256");
    p.setPersonalId("777-216");
    Mapper mapper=conn.openSession();
    try {
        System.out.println("All set to go");
        mapper.saveOrUpdatePerson(p);
    } finally {
        conn.closeSession();
    }

Stacktrace is the following:

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error opening session.  Cause: java.lang.NullPointerException
### The error may exist in org/abondar/experimental/mybatisdemo/mappers/Mapper.java (best guess)
### Cause: java.lang.NullPointerException
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSessionFromDataSource(DefaultSqlSessionFactory.java:100)
    at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSession(DefaultSqlSessionFactory.java:47)
    at org.abondar.experimental.mybatisdemo.SetDBConnection.openSession(SetDBConnection.java:51)
    at org.abondar.experimental.mybatisdemo.Main.main(Main.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: java.lang.NullPointerException
    at org.apache.ibatis.session.defaults.DefaultSqlSessionFactory.openSessionFromDataSource(DefaultSqlSessionFactory.java:95)
    ... 8 more

What can be wrong and is there any way not to re-establish DB-connection for every action(select,insert or delete)?

Well, looking at the stack trace you posted, it happens on line 51 of SetDBConnection. We can't see line numbers. What line is that, then? — OneCricketeer
– OneCricketeer, Commented Feb 3, 2016 at 13:17
@cricket_007 that's the line 51: session = sqlSessionFactory.openSession(); — fghf
– fghf, Commented Feb 3, 2016 at 13:23

Frank · Accepted Answer · 2016-02-03 13:47:30Z

4

It seems you have no Environment and TransactionFactory defined. According to the docs you should initialize MyBatis somehow like this:

DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();
TransactionFactory transactionFactory = new JdbcTransactionFactory();
Environment environment = new Environment("development", transactionFactory, dataSource); 
Configuration configuration = new Configuration(environment);

answered Feb 3, 2016 at 13:47

Frank

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2 Comments

fghf Over a year ago

But what is BlogDataSourceFactory?

Frank Over a year ago

It's the DataSourceFactory-Implementation used in the example. As stated in the docs "You can plug any 3rd party DataSource by implementing the interface org.apache.ibatis.datasource.DataSourceFactory". Essential is that you have a valid DataSource at this point.

fghf · Accepted Answer · 2016-02-03 14:14:44Z

0

Thanks Frank for DataSource idea. I used default pooled dataSource and this problem looks to be solved

answered Feb 3, 2016 at 14:14

fghf

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