JavaEE(9) - Session EJB的生命周期、事务及拦截器

时间：2021-11-08 16:17:53

1. SessionBean的生命周期

无状态Session Bean: 不存在状态-->待命状态-->被销毁状态

不存在状态-->待命状态：

1）通过构造器创建EJB实例

2）执行依赖注入

3）执行@PostConstruct回调方法

待命状态-->被销毁状态

1）执行@PreDestroy回调方法

有状态Session Bean: 不存在状态-->待命状态(<-->去活状态-->被销毁状态)-->被销毁状态

不存在状态-->待命状态：

1）通过构造器创建EJB实例

2）执行依赖注入

3）执行@PostConstruct回调方法

待命状态-->去活状态

1）执行@PrePassive回调方法

去活状态-->待命状态

1）执行@PostActivate回调方法

待命状态-->被销毁状态

1）客户端调用@Remove方法

2）执行@PreDestroy回调方法

#1. 开发EJB(Net Beans创建EJB Module, 项目名称：Lifecycle)

ShopService.java

package org.crazyit.service;

import javax.ejb.*;

import java.util.*;

@Remote

public interface ShopService {

    void addItem(String item);

    Map<String, Integer> showDetail();

    void remove();

}

ShopServiceBean.java

package org.crazyit.service;

import java.util.*;

import javax.annotation.PostConstruct;

import javax.annotation.PreDestroy;

import javax.ejb.*;

@Stateful(mappedName = "ShopService")

public class ShopServiceBean implements ShopService {

    private Map<String, Integer> buyInfo = new HashMap<String, Integer>();

    public void addItem(String item) {

        //该物品已经购买过

        if (buyInfo.containsKey(item)) {

            buyInfo.put(item, buyInfo.get(item) + 1);

        } else {

            buyInfo.put(item, 1);

        }

    }

    public Map<String, Integer> showDetail() {

        return buyInfo;

    }

    @Remove

    public void remove() {

        System.out.println("执行@Remove修饰的方法!");

    }

    //下面定义了5个简单的生命周期方法

    @Init

    public void init() {

        System.out.println("执行@Init修饰的方法!");

    }

    @PostConstruct

    public void postConstruct() {

        System.out.println("执行@PostConstruct修饰的方法!");

    }

    @PrePassivate

    public void prePassivate() {

        System.out.println("执行@PrePassivate修饰的方法!");

    }

    @PostActivate

    public void postActivate() {

        System.out.println("执行@PostActivate修饰的方法!");

    }

    @PreDestroy

    public void preDestroy() {

        System.out.println("执行@PreDestroy修饰的方法!");

    }

}

#2. 客户端调用EJB (参见8.5)

2. 容器管理事务

#1. EJB开发(Net Beans创建EJB Module, 项目名称：CMT)

Cmt.java

package org.crazyit.service;

import javax.ejb.Remote;

@Remote

public interface Cmt {

    void insert();

}

CmtBean.java

package org.crazyit.service;

import java.sql.Connection;

import java.sql.SQLException;

import java.sql.Statement;

import javax.annotation.Resource;

import javax.ejb.*;

import javax.naming.Context;

import javax.naming.InitialContext;

import javax.naming.NamingException;

import javax.sql.DataSource;

@Stateless(mappedName = "cmt")

@TransactionManagement(TransactionManagementType.CONTAINER)

@TransactionAttribute(TransactionAttributeType.REQUIRED)

public class CmtBean implements Cmt {

    private DataSource ds = null;

    @Resource

    private SessionContext sessCtx;

    public CmtBean() throws NamingException {

        Context ctx = new InitialContext();

        ds = (DataSource) ctx.lookup("javaee");

    }

    public void insert() {

        try {

            Connection conn = ds.getConnection();

            Statement stmt = conn.createStatement();

            int result = stmt.executeUpdate("insert into user_table values(null, '新用户' , 'bbb')");

            System.out.println(result);

            //下面这条语句将引起失败

            stmt.executeUpdate("insert into user_table values(1, 'aaa' , 'bbb')");

            stmt.close();

            conn.close();

        }

        catch (SQLException ex) {

            ex.printStackTrace();

            sessCtx.setRollbackOnly();

        }

    }

}

#2. 客户端调用EJB (Net Beans创建Java Project: CmtTest)

Cmt.java

package org.crazyit.service;

public interface Cmt {

    void insert();

}

EjbClient.java

package lee;

import javax.rmi.*;

import javax.naming.*;

import java.util.Properties;

import org.crazyit.service.*;

public class EjbClient {

    public void test() throws NamingException {

        //获取WebLogic中JNDI服务的Context

        Context ctx = getInitialContext();

        Cmt cmt = (Cmt) ctx.lookup("Cmt#org.crazyit.service.Cmt");

        cmt.insert();

    }

    //工具方法，用来获取WebLogic中JNDI服务的Context

    private Context getInitialContext() {

        // 参见(4)

    }

    public static void main(String[] args) throws Exception {

        EjbClient client = new EjbClient();

        client.test();

    }

}

3. Bean管理事务

#1. EJB开发(Net Beans创建EJB Module, 项目名称：BMT)

Bmt.java

package org.crazyit.service;

import javax.ejb.Remote;

@Remote

public interface Bmt {

    void insert() throws Exception;

}

BmtBean.java

package org.crazyit.service;

import java.util.*;

import javax.ejb.*;

import javax.annotation.*;

import javax.naming.*;

import java.sql.*;

import javax.sql.*;

import javax.transaction.*;

@Stateless(mappedName = "bmt")

@TransactionManagement(TransactionManagementType.BEAN)

public class BmtBean implements Bmt {

    private DataSource ds = null;

    @Resource

    private UserTransaction trans;

    public BmtBean() throws NamingException {

        Context ctx = new InitialContext();

        ds = (DataSource) ctx.lookup("javaee");

    }

    public void insert() throws Exception {

        try {

            //开始事务

            trans.begin();

            Connection conn = ds.getConnection();

            Statement stmt = conn.createStatement();

            int result = stmt.executeUpdate("insert into user_table values(null, 'BMT插入的记录' , 'bbb')");

            System.out.println(result);

            //下面这条语句将引起失败

            stmt.executeUpdate("insert into user_table values(1, 'aaa' , 'bbb')");

            //提交事务

            trans.commit();

            stmt.close();

            conn.close();

        }

        catch (SQLException ex) {

            ex.printStackTrace();

            //回滚事务

            trans.rollback();

        }

    }

}

#2. 客户端调用EJB (Net Beans创建Java Project: BmtTest)

Bmt.java

package org.crazyit.service;

public interface Bmt {

    void insert() throws Exception;

}

EjbClient.java

package lee;

import javax.rmi.*;

import javax.naming.*;

import java.util.Properties;

import org.crazyit.service.*;

public class EjbClient {

    public void test() throws Exception {

        //获取WebLogic中JNDI服务的Context

        Context ctx = getInitialContext();

        Bmt bmt = (Bmt) ctx.lookup("Bmt#org.crazyit.service.Bmt");

        bmt.insert();

    }

    //工具方法，用来获取WebLogic中JNDI服务的Context

    private Context getInitialContext() {

        // 参见(4)

    }

    public static void main(String[] args) throws Exception {

        EjbClient client = new EjbClient();

        client.test();

    }

}

4. 拦截器

#1. EJB开发(Net Beans创建EJB Module, 项目名称：Interceptor)

MyInterceptor.java

package org.crazyit.interceptor;

import javax.interceptor.AroundInvoke;

import javax.interceptor.InvocationContext;

public class MyInterceptor {

    @AroundInvoke

    public Object log(InvocationContext ctx) throws Exception {

        System.out.println("------拦截器开始运行------");

        //让目标方法执行

        Object rvt = ctx.proceed();

        if (rvt != null) {

            rvt = "拦截器改变了返回值：" + rvt;

        }

        System.out.println("------拦截器执行结束------");

        return rvt;

    }

}

HelloCrazyit.java

package org.crazyit.service;

import javax.ejb.*;

@Remote

public interface HelloCrazyit{

    String hello(String name);

    void crazyit();

    void exclude();

}

HelloCrazyitBean.java

package org.crazyit.service;

import java.util.*;

import javax.ejb.*;

import javax.annotation.*;

import javax.interceptor.*;

import org.crazyit.interceptor.*;

@Stateless(mappedName = "HelloCrazyit")

@Interceptors(MyInterceptor.class)

public class HelloCrazyitBean implements HelloCrazyit {

    public String hello(String name) {

        System.out.println(name + ", 您好！现在时间是：" + new java.util.Date());

        return "crazyit.org";

    }

    public void crazyit() {

        System.out.println("疯狂Java联盟!");

        System.out.println("最受欢迎的Java论坛!");

    }

    @ExcludeClassInterceptors

    public void exclude() {

        System.out.println("被排除在拦截器机制之外的方法!");

    }

}

#2. 客户端调用EJB (Net Beans创建Java Project: InterceptorTest)

HelloCrazyit.java

package org.crazyit.service;

public interface HelloCrazyit {

    String hello(String name);

    void crazyit();

    void exclude();

}

EjbClient.java

package lee;

import javax.rmi.*;

import javax.naming.*;

import java.util.Properties;

import org.crazyit.service.*;

public class EjbClient {

    public void test()

            throws Exception {

        //获取WebLogic中JNDI服务的Context

        Context ctx = getInitialContext();

        HelloCrazyit bmt = (HelloCrazyit) ctx.lookup("HelloCrazyit#org.crazyit.service.HelloCrazyit");

        System.out.println(bmt.hello("yeeku"));

        bmt.crazyit();

        bmt.exclude();

    }

    //工具方法，用来获取WebLogic中JNDI服务的Context

    private Context getInitialContext() {

        // 参见(4)

    }

    public static void main(String[] args) throws Exception {

        EjbClient client = new EjbClient();

        client.test();

    }

}

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