Kohei Nozaki's blog 

Lean example of Tomcat 8 + Guice 4 + Jersey 2.19

Posted on Wednesday Aug 05, 2015 at 02:36PM in Technology

Jersey is the RI of JAX-RS. in this entry, I introduce you how to use Jersey 2.19 with Guice 4 on Tomcat 8. it looks like there are some issues exist as follows but thanks to https://github.com/Squarespace/jersey2-guice , I’ve succeeded to use them anyway.

The entire project which based on Maven can be obtained from My GitHub repository.

Dependencies

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.glassfish.jersey</groupId>
            <artifactId>jersey-bom</artifactId>
            <version>2.19</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet</artifactId>
    </dependency>
    <dependency>
        <groupId>com.google.inject</groupId>
        <artifactId>guice</artifactId>
        <version>4.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.inject.extensions</groupId>
        <artifactId>guice-servlet</artifactId>
        <version>4.0</version>
    </dependency>
    <dependency>
        <groupId>com.squarespace.jersey2-guice</groupId>
        <artifactId>jersey2-guice</artifactId>
        <version>0.10</version>
    </dependency>
</dependencies>

web.xml

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>guice.tomcat.jersey</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>Jersey Web Application</servlet-name>
        <url-pattern>/webapi/*</url-pattern>
    </servlet-mapping>

    <listener>
        <listener-class>guice.tomcat.MyJerseyGuiceServletContextListener</listener-class>
    </listener>

    <filter>
        <filter-name>guiceFilter</filter-name>
        <filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>guiceFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

MyJerseyGuiceServletContextListener.java

In this example, we use the servlet context listener named JerseyGuiceServletContextListener which comes from jersey2-guice artifact as parent class.

public class MyJerseyGuiceServletContextListener extends JerseyGuiceServletContextListener {
    @Override
    protected List<? extends Module> modules() {
        return Collections.singletonList(new ServletModule() {
            @Override
            protected void configureServlets() {
                bind(MyService.class).to(MyServiceImpl.class);
            }
        });
    }
}

Service class

We use very simple pair of an interface and implementation that creates a simple greeting message, which used in a past entry so omitted for simplicity.

MyResource.java

This is an simple implementation of JAX-RS resource class. placed under guice.tomcat.jersey package. the preceding service class named MyService will be injected by @javax.inject.Inject annotation.

@Path("myresource")
public class MyResource {

    @Inject
    private MyService myService;

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getIt() {
        return myService.hello("Jersey");
    }
}

Test run

$ curl http://localhost:8080/webapi/myresource
Hello, Jersey

Comments [8]

Tags: guice jersey tomcat

Lean example of Tomcat 8 + Guice 4 + EclipseLink 2.6.0

Posted on Tuesday Aug 04, 2015 at 07:26PM in Technology

I wrote a Lean example of Tomcat 8 + Guice 4 in previous entry. this time, I’ll try JPA(EclipseLink) integration with automatic transaction management.

The entire project which based on Maven can be obtained from My GitHub repository.

Prerequisites

For database connection, we’ll use a DataSource which is defined on Tomcat server. to define a Embedded Derby DataSource, This entry would help.

Dependencies

<dependencies>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.eclipse.persistence</groupId>
        <artifactId>eclipselink</artifactId>
        <version>2.6.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.inject</groupId>
        <artifactId>guice</artifactId>
        <version>4.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.inject.extensions</groupId>
        <artifactId>guice-servlet</artifactId>
        <version>4.0</version>
    </dependency>
    <dependency>
        <groupId>com.google.inject.extensions</groupId>
        <artifactId>guice-persist</artifactId>
        <version>4.0</version>
    </dependency>
</dependencies>

web.xml

No changes against previous entry except addition of resource-ref element.

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <!-- taken from https://github.com/google/guice/wiki/Servlets -->

    <listener>
        <listener-class>guice.tomcat.MyGuiceServletConfig</listener-class>
    </listener>

    <filter>
        <filter-name>guiceFilter</filter-name>
        <filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>guiceFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <resource-ref>
        <res-ref-name>jdbc/derby</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

</web-app>

META-INF/persistence.xml

If you don’t want to use a DataSource on Tomcat, specify the connection information in javax.persistence.jdbc.* properties instead of non-jta-data-source.

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="myJpaUnit" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <non-jta-data-source>java:comp/env/jdbc/derby</non-jta-data-source>
        <class>guice.tomcat.MyEntity</class>
        <properties>
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
            <property name="eclipselink.logging.level" value="FINE"/>
            <property name="eclipselink.logging.level.sql" value="FINE"/>
        </properties>
    </persistence-unit>
</persistence>

MyGuiceServletConfig.java

The last two statements will take care of JPA integration.

public class MyGuiceServletConfig extends GuiceServletContextListener {
    @Override
    protected Injector getInjector() {
        return Guice.createInjector(new ServletModule() {
            @Override
            protected void configureServlets() {
                serve("/*").with(MyServlet.class);
                bind(MyService.class).to(MyServiceImpl.class);

                install(new JpaPersistModule("myJpaUnit"));
                filter("/*").through(PersistFilter.class);
            }
        });
    }
}

MyEntity.java

This is a very simple JPA entity which keeps only generated id and ts (a timestamp).

@Entity
@NamedQuery(name = "MyEntity.findAll", query = "SELECT e FROM MyEntity e ORDER BY e.id DESC")
public class MyEntity implements Serializable {

    @Id
    @GeneratedValue
    private Long id;
    @Column(nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    private Date ts;

... accessors are omitted

Service class

MyService.java

public interface MyService {
    void save(MyEntity e);
    List<MyEntity> findAll();
}

MyServiceImpl.java

Note that you need to annotate a method with @com.google.inject.persist.Transactional if you need a transaction on it.

public class MyServiceImpl implements MyService {

    // Transactions doesn't start if EntityManager is directly injected via @Inject.
    // I have no idea why...

    // According to https://github.com/google/guice/wiki/JPA,
    // "Note that if you make MyService a @Singleton, then you should inject Provider<EntityManager> instead."
    @Inject
    private Provider<EntityManager> emp;

    @Override
    // @javax.transaction.Transactional is not supported yet. https://github.com/google/guice/issues/797
    @com.google.inject.persist.Transactional
    public void save(MyEntity e) {
        EntityManager em = emp.get();
        em.persist(e);
    }

    @Override
    public List<MyEntity> findAll() {
        return emp.get().createNamedQuery("MyEntity.findAll", MyEntity.class).getResultList();
    }
}

MyServlet.java

This servlet saves a MyEntity with current timestamp, then fetches all of rows and returns them to the client on every request.

@javax.inject.Singleton
public class MyServlet extends HttpServlet {

    @javax.inject.Inject
    private MyService myService;

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        MyEntity myEntity = new MyEntity();
        myEntity.setTs(new Date());
        myService.save(myEntity);

        PrintWriter writer = resp.getWriter();
        writer.write("<html><body><ul>");
        for(MyEntity e : myService.findAll()){
            writer.write("<li>");
            writer.write(e.toString());
            writer.write("</li>");
        }
        writer.write("</ul></body></html>");

    }
}

Test run

A row will be saved on every request as follows:

4d678c4b c55c 41e0 ba5d 65d2832409fb

References

Comments [0]

Tags: eclipselink guice jpa tomcat

Lean example of Tomcat 8 + Guice 4

Posted on Monday Aug 03, 2015 at 06:56PM in Technology

I prefer Java EE stack usually, but I need to learn a Tomcat based stack for some reasons these days. in this entry, I introduce you a very simple example of Tomcat 8 + Guice 4 app which uses GuiceFilter and GuiceServletContextListener so that bring Guice to a Servlet based web application.

The entire project which based on Maven can be obtained from My GitHub repository.

Dependencies

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>com.google.inject</groupId>
    <artifactId>guice</artifactId>
    <version>4.0</version>
</dependency>
<dependency>
    <groupId>com.google.inject.extensions</groupId>
    <artifactId>guice-servlet</artifactId>
    <version>4.0</version>
</dependency>

web.xml

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <listener>
        <listener-class>guice.tomcat.MyGuiceServletConfig</listener-class>
    </listener>

    <filter>
        <filter-name>guiceFilter</filter-name>
        <filter-class>com.google.inject.servlet.GuiceFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>guiceFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

MyGuiceServletConfig.java

We need to declare servlet mappings and the mappings between interfaces and implementations here.

public class MyGuiceServletConfig extends GuiceServletContextListener {
    @Override
    protected Injector getInjector() {
        return Guice.createInjector(new ServletModule() {
            @Override
            protected void configureServlets() {
                serve("/*").with(MyServlet.class);
                bind(MyService.class).to(MyServiceImpl.class);
            }
        });
    }
}

Service class

We use a pair of a very simple implementation of a service class. it simply creates a greetings which uses an argument.

MyService.java

public interface MyService {
    String hello(String name);
}

MyServiceImpl.java

public class MyServiceImpl implements MyService {
    @Override
    public String hello(String name) {
        return "Hello, " + name;
    }
}

MyServlet.java

Note that we use @javax.inject.Singleton and @javax.inject.Inject annotations, that are standardized JSR API.

@javax.inject.Singleton
public class MyServlet extends HttpServlet {

    @javax.inject.Inject
    private MyService myService;

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write(myService.hello("Guice"));
    }
}

Test run

After deployment, send a request to check the response:

$ curl http://localhost:8080
Hello, Guice

Other things/functions need to be studied

  • Transaction management

  • CDI Producer equivalent

  • AOP

  • Automatic implementation scanning/binding

References

Comments [1]

Tags: guice tomcat

Purchased book list in O'Reilly's 60% off sale

Posted on Thursday May 07, 2015 at 05:34PM in Technology

Total: $170.38 USD

  • SQL and Relational Theory, 2nd Edition

  • CSS Secrets

  • Professional Java EE Design Patterns

  • Java Performance: The Definitive Guide

  • Java 8 Lambdas

  • Java Cookbook, 3rd Edition

  • Learning Java, 4th Edition

  • RESTful Java with JAX-RS 2.0, 2nd Edition

  • Continuous Enterprise Development in Java

  • Head First Servlets and JSP, 2nd Edition

  • Head First HTML and CSS, 2nd Edition

Comments [0]

Configuring Apache James to use PostgreSQL as the backend

Posted on Sunday Apr 19, 2015 at 09:37PM in Technology

UPDATE: I’m running into a strange problem of using PostgreSQL as backend with Thunderbird. I recommend to use an other database as the backend at the moment. http://www.mail-archive.com/server-user%40james.apache.org/msg14715.html

UPDATE2: I created a patch to solve the issue and it seems fine. for detail and download the patch see: https://issues.apache.org/jira/browse/MAILBOX-228

I have been used Apache James with Embedded Derby, but its CPU/IO consumption is increasing day by day. I’m not sure where is the bottleneck but I decided to move to PostgreSQL as its backend anyway.

  1. Put JDBC driver (I used postgresql-9.3-1100.jdbc41.jar) into $JAMES_HOME/conf/lib

  2. Create james-database.properties from template, and put it into $JAMES_HOME/conf as follows

    database.driverClassName=org.postgresql.Driver
database.url=jdbc:postgresql://127.0.0.1:5432/james
database.username=james
database.password=***

vendorAdapter.database=POSTGRESQL

openjpa.streaming=true

  3. Restart James instance

  4. Create domains, addresses and aliases:

    ./james-cli.sh -h localhost -p 9999 adddomain example.org
./james-cli.sh -h localhost -p 9999 adduser kyle@example.org ***
./james-cli.sh -p 9999 -h localhost addaddressmapping postmaster example.org kyle@example.org

Note

This guide claims that setting standard_conforming_strings=off is needed, but I guess this issue may address this problem, so I don’t use this setting at the moment. my James installation is shipped with openjpa-2.2.1.jar and the issue was fixed in 2.2.0.

Comments [3]

Tags: james postgres

About Me

Java backend engineer obsessed with test driven development. Apache Roller committer. kohei at apache dot org

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