Spring Batch 初始化數據，清空數據的做法

這兩天用了一下Spring Batch來導數據，感覺是個很強大的工具。網上的資料很多，沒看到連續運行的示例。從mkong和spring官網上搞了幾段代碼，在本地跑了一下發現幾個問題：

1. initialize-database執行官方的drop table失敗

報權限問題，檢查了一下，無法就是清理spring batch任務表中的數據

DROP TABLE  BATCH_STEP_EXECUTION_CONTEXT ;
DROP TABLE  BATCH_JOB_EXECUTION_CONTEXT ;
DROP TABLE  BATCH_STEP_EXECUTION ;
DROP TABLE  BATCH_JOB_EXECUTION_PARAMS ;
DROP TABLE  BATCH_JOB_EXECUTION ;
DROP TABLE  BATCH_JOB_INSTANCE ;

DROP TABLE  BATCH_STEP_EXECUTION_SEQ ;
DROP TABLE  BATCH_JOB_EXECUTION_SEQ ;
DROP TABLE  BATCH_JOB_SEQ ;

其實多次執行的時候不用drop這個表，所以將這塊去掉了，改成了由

<jdbc:script location="classpath:init.sql" />

調用一段本地的腳本

2. 連續運行job失敗

這個是傳參的問題，每次給JobParameters設置不同的參數才能順利的連續運行。

HashMap<String, JobParameter> parameters = new HashMap<String, JobParameter>();
parameters.put("currentTime", new JobParameter(System.currentTimeMillis()));
JobExecution execution = jobLauncher.run(job, new JobParameters(parameters));

加了個當前時間，搞定

3.第二次執行導入的時候報主鍵錯誤

因爲每次都是完全拷貝，沒做檢查，所以在插入前有必要清理所有的內容。可是程序在多次運行（注意，是連續運行）的情況下，只會運行一次initialize-database的內容。

翻遍了例子所有的step都要有reader和writer。於是手動寫了一個Reader和Writer來跑清理的過程。注意還要寫一個Listener，不然會一直執行下去，這個是用來讓計數器歸位的。

job的配置

<batch:tasklet transaction-manager="transactionManagerJob">
    <batch:chunk reader="deleteReader" writer="deleteWriter"
					commit-interval="1">
    </batch:chunk>
    <batch:listeners>
        <batch:listener ref="resettingListener"/>
    </batch:listeners>
</batch:tasklet>

reader的配置

<beans:bean id="deleteReader" class="xxx.InitReader">
    <property name="limit" value="1"/>
</beans:bean>

writer的配置

<beans:bean id="deleteWriter" class="xxxx.InitWriter">
    <property name="dataSource" ref="targetDataSource" />
    <property name="sql"
			value="
DELETE FROM XXX;
DELETE FROM YYY;
			" />
</beans:bean>

listener的配置

<beans:bean id="resettingListener" class="xxx.InitResettingListener">
    <beans:property name="reader" ref="deleteReader" />
</beans:bean>

reader的代碼

public class InitReader extends ItemReaderAdapter<Object> {
	private int limit = 1;
	private int counter = 0;
	
	public Object read() throws Exception, UnexpectedInputException, ParseException {
		if(counter<limit){
			counter++;
			return new Object();
		}
		return null;
	}
	
	/**
	 * @param limit number of items that will be generated
	 * (null returned on consecutive calls).
	 */
	public void setLimit(int limit) {
		this.limit = limit;
	}

	public int getCounter() {
		return counter;
	}

	public int getLimit() {
		return limit;
	}

	public void resetCounter()
	{
		this.counter = 0;
	}
	
	 public void afterPropertiesSet() throws Exception {
	     Assert.notNull(limit, "limit must be set");
	 }
}

writer的代碼

public class InitWriter extends ItemWriterAdapter<Object>{
	private DriverManagerDataSource dataSource;
	private String sql;
	
	
	public DriverManagerDataSource getDataSource() {
		return dataSource;
	}

	public void setDataSource(DriverManagerDataSource dataSource) {
		this.dataSource = dataSource;
	}

	public String getSql() {
		return sql;
	}

	public void setSql(String sql) {
		this.sql = sql;
	}
	
	public void write(List<? extends Object> items) throws Exception {
		//System.out.println("init write delete");
		Connection connection = dataSource.getConnection();
		PreparedStatement preparedStatement=connection.prepareStatement(sql);
		preparedStatement.executeUpdate();
		System.out.println("init delete data complete.");
	}
	
	public void afterPropertiesSet() throws Exception {
	    Assert.notNull(dataSource, "dataSource limit must be set");
	    Assert.notNull(sql, "sql limit must be set");
	}
}

listener的代碼

public class InitResettingListener extends StepExecutionListenerSupport implements InitializingBean {

	private InitReader reader;

	public ExitStatus afterStep(StepExecution stepExecution) {
		this.reader.resetCounter();
		return null;
	}

	public void setReader(InitReader reader) {
		this.reader = reader;
	}

	public void afterPropertiesSet() throws Exception {
		Assert.notNull(this.reader, "The 'reader' must be set.");
	}
}

搞定！！！