上面介紹了Spring Batch的基本概念和簡單的demo專案，顯然這些還是不夠實際使用的。下面我們來更多的程式碼實踐。

        在上面的基礎專案上面，我們來更多的修改：

        不用專案預設的hsql DB，用mysql,讓ItemReader,ItemWriter 支援mysql；

        支援處理結果自定義儲存到資料庫，我們用專案裡面的JPA；

        讓Quartz來定時呼叫spring batch的Job

        可以讀取檔案，而不只是資料庫；

下面開始動手。

          修改pom.xml，節選部分，實在太長了。

          <spring.framework.version>3.2.0.RELEASE</spring.framework.version>
          <spring.batch.version>2.1.7.RELEASE</spring.batch.version>   <!--  這個的版本和quartz的版本要注意，不然很容易在執行的時候出錯 -->

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.23</version>
</dependency>
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-jpa</artifactId>
<version>1.3.2.RELEASE.rebuild</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.6.10.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>3.6.10.Final</version>
</dependency>
<dependency>
<groupId>org.quartz-scheduler</groupId>
<artifactId>quartz</artifactId>
<version>2.1.7</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>3.2.0.RELEASE</version>
</dependency>

launch-context.xml定義需要用到的bean,

<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitName" value="spring" />
<property name="dataSource" ref="dataSource" />
<property name="jpaDialect">
    <bean class="com.test.batch.CustomHibernateJpaDialect" />
  </property>
<property name="loadTimeWeaver">
<bean
class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />
</property>
</bean>
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/testbatch?useUnicode=true&amp;characterEncoding=UTF-8&amp;autoReconnect=true" />
<property name="username" value="root" />
<property name="password" value="root" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
<property name="dataSource" ref="dataSource" />
</bean>
<bean id="customerMapper" class="com.test.batch.CustomerMapper"></bean>
<bean id="lineTokenizer" class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer"></bean>
        <!--   這個可以讓spring batch和hibernate共用
<bean id="itemReader"
class="org.springframework.batch.item.database.HibernateCursorItemReader">
<property name="sessionFactory" ref="sessionFactory" />
<property name="queryString" value="from CustomerCredit" />
</bean>
-->
<bean id="itemReaderFile" class="org.springframework.batch.item.file.FlatFileItemReader" scope="step">
<property name="lineMapper">
<bean class="org.springframework.batch.item.file.mapping.DefaultLineMapper">
<property name="lineTokenizer" ref="lineTokenizer"/>
<property name="fieldSetMapper" ref="customerMapper"/>
</bean>   
</property>
<!--<property name="resource" value="file:#{jobParameters['customFileAbPath']}"/>   配置讀取檔案的路徑，我固定了       -->
<property name="resource" value="file:D:/temp/testdata.txt"/>
</bean>
<bean id="itemReader" class="org.springframework.batch.item.database.JdbcCursorItemReader">
    <property name="dataSource" ref="dataSource"/>
    <property name="sql" value="select ID, NAME, CREDIT from CUSTOMER"/>
    <property name="rowMapper">
        <bean class="com.test.batch.CustomerCreditRowMapper"/>
    </property>
    <property name="fetchSize" value="100"></property>
    <property name="maxRows" value="10000"></property>
</bean>

<jdbc:initialize-database data-source="dataSource">
<!-- <jdbc:script location="${batch.schema.script}" /> -->
<jdbc:script location="org/springframework/batch/core/schema-drop-mysql.sql" />
<jdbc:script location="org/springframework/batch/core/schema-mysql.sql" />
</jdbc:initialize-database

<!-- batch:job-repository id="jobRepository" / -->
<batch:job-repository id="jobRepository"
data-source="dataSource" transaction-manager="transactionManager"
isolation-level-for-create="SERIALIZABLE" table-prefix="BATCH_" />
        <!-- 下面是Quartz呼叫spring batch 的job要用到的 -->
        <bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
<property name="triggers">
<list><ref bean="scheduledTrigger"></ref></list>
</property>
</bean>

<bean id="scheduledTrigger" class="org.springframework.scheduling.quartz.CronTriggerFactoryBean">
    <property name="jobDetail" ref="jobDetail"/>
   <property name="cronExpression">
        <value>*/10 * * * * ?</value>
    </property>
</bean>

<bean id="jobDetail" class="org.springframework.scheduling.quartz.JobDetailFactoryBean">
<property name="jobClass" value="com.test.batch.JobLauncherDetails" />
<property name="jobDataAsMap">
<map>
<entry key="jobName" value="job1" />  <!--指定jobID -->
<entry key="jobLocator" value-ref="jobRegistry" />
<entry key="jobLauncher" value-ref="jobLauncher" />
<entry key="param1" value="p1" />
<entry key="param2" value="p2" />
</map>
</property>
<property name="durability" value="true" />
</bean>

        <bean id="jobLauncher"
class="org.springframework.batch.core.launch.support.SimpleJobLauncher">
<property name="jobRepository" ref="jobRepository" />
  </bean>

  <bean
class="org.springframework.batch.core.configuration.support.JobRegistryBeanPostProcessor">
<property name="jobRegistry" ref="jobRegistry" />
       </bean>

       <bean id="jobRegistry" class="org.springframework.batch.core.configuration.support.MapJobRegistry" />

<import resource="classpath:/META-INF/spring/module-context.xml" />

有幾個定製的東西，需要說下。

我們用到的domain物件是這樣的，很多不必要的都省略了

@Entity
@Table(name = "customer")
public class CustomerCredit {
public static final String TABLE_NAME = "customer";

@Column(name = "name", nullable = true, length = 12)
private String name;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", nullable = false)
private Integer id;

@Column(name = "credit", nullable = true, precision = 15, scale = 2)
private BigDecimal credit;

FlatFileItemReader 使用預設的DefaultLineMapper，裡面指定了lineTokenizer和fieldSetMapper，就是說要怎麼讀一行行的資料，讀了之後怎麼和Bean的欄位Mapper，這樣後面的步驟好繼續處理。

public class CustomerMapper implements FieldSetMapper<CustomerCredit> {
@Override
public CustomerCredit mapFieldSet(FieldSet fieldSet) throws BindException {
CustomerCredit lv = new CustomerCredit();
lv.setId(Integer.parseInt(fieldSet.readString(0)));
lv.setName(fieldSet.readString(1));
lv.setCredit(fieldSet.readBigDecimal(2));
return lv;
}
}

如果是讀資料庫呢？就是下面那個JdbcCursorItemReader，裡面指定了dataSource，sql，rowMapper，這些都類似檔案

public class CustomerCreditRowMapper implements RowMapper {
    public static final String ID_COLUMN = "id";
    public static final String NAME_COLUMN = "name";
    public static final String CREDIT_COLUMN = "credit";

    public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
        CustomerCredit customerCredit = new CustomerCredit();
        customerCredit.setId(rs.getInt(ID_COLUMN));
        customerCredit.setName(rs.getString(NAME_COLUMN));
        customerCredit.setCredit(rs.getBigDecimal(CREDIT_COLUMN));
        return customerCredit;
    }
}

還可以和hibernate結合來讀取資料，可以讀取儲存過程的資料，等等，具體可以參考spring batch文件

說好的自定義處理資料呢，比如我們把每個人的Credit加10.

@Component("customProcessor")
public class CustomProcessor implements
ItemProcessor<CustomerCredit, CustomerCredit> {
@PersistenceContext
private EntityManager em;
@Override
public CustomerCredit process(CustomerCredit item) throws Exception {
System.out.println(new Date().toString()+"start to process");
if (item == null) {
return null;
}
try {
item = em.find(CustomerCredit.class, item.getId());
item.setCredit(item.getCredit().add(new BigDecimal(10)));
//find by id才可以persist (否則出現detached entity passed to persist)
em.persist(item);
} catch (Exception e) {
e.printStackTrace();
}
return item;
}
}

每一步的處理，我們想看看結果，可以定製一個ItemReadListener

public class CustomStepListener implements ItemReadListener<CustomerCredit>   具體程式碼省略

修改module-context.xml

<batch:job id="job1">
<batch:step id="step1">
<batch:tasklet transaction-manager="transactionManager"
start-limit="100">
<batch:chunk reader="itemReade" writer="itemwriter" processor="customProcessor" 
commit-interval="3" />
</batch:tasklet>
</batch:step>
</batch:job>

在META-INF下面加個persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="spring" transaction-type="RESOURCE_LOCAL">
<!-- 
<class>com.test.jpatest.model.Customer</class>
<class>com.test.jpatest.model.Address</class>
-->
<provider>org.hibernate.ejb.HibernatePersistence</provider>
</persistence-unit>
</persistence>

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'exampleConfiguration': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.springframework.batch.core.repository.JobRepository com.test.batch.ExampleConfiguration.jobRepository; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jobRepository': Cannot resolve reference to bean 'transactionManager' while setting bean property 'transactionManager'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager' defined in class path resource [launch-context.xml]: Cannot resolve reference to bean 'entityManagerFactory' while setting bean property 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [launch-context.xml]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: No persistence unit with name 'spring' found

執行的時候遇到上面的錯誤，就是沒有上面的配置的原因

org.springframework.transaction.InvalidIsolationLevelException: Standard JPA does not support custom isolation levels - use a special JpaDialect for your JPA implementation
at org.springframework.orm.jpa.DefaultJpaDialect.beginTransaction(DefaultJpaDialect.java:66)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.beginTransaction(HibernateJpaDialect.java:59)

遇到這樣的錯誤，是因為預設的JPA不支援自定義的事物隔離級別。可以自定義一個CustomHibernateJpaDialect extends HibernateJpaDialect，具體程式碼沒有列出，可以找下。

在用Quartz的時候遇到

Caused by: java.lang.IncompatibleClassChangeError: class org.springframework.scheduling.quartz.CronTriggerBean has interface org.quartz.CronTrigger as super class  

這個是由於網上的很多例子都是quartz版本稍舊的原因，我用的是quartz 2.1.7

錯誤：Jobs added with no trigger must be durable
<property name="durability" value="true" />  

坑真的是不少，需要一個個解決。最後測試一下，是不是定時執行我們的job：

public class App {
public static void main(String[] args) {
String springConfig = "launch-context.xml";
ApplicationContext context = new ClassPathXmlApplicationContext(
springConfig);
}
}

祝你好運，能夠成功，。