Mybatis實踐--Mybatis Generator 獲取不到字段註釋

Mybatis Generator 獲取不到字段註釋 

前言

環境限制,暫時只提供Oracle和Mysql的解決方法,其它數據庫若是遇到一樣問題,原理是同樣的,具體就看該數據庫應當去配置哪一個屬性.

解決方法

下面的配置均指的是Mybatis Generator 的配置文件(通常是叫generatorConfig.xml)的配置:

Oracle 數據庫

<jdbcConnection driverClass="${driver}"
    connectionURL="{url}" userId="${username}" password="${password}">
    <!-- 針對oracle數據庫 -->
    <property name="remarksReporting" value="true"></property>
</jdbcConnection>

MySql 數據庫

方法1

<jdbcConnection driverClass="${driver}"
    connectionURL="{url}" userId="${username}" password="${password}">
    <!-- 針對mysql數據庫 -->
    <property name="useInformationSchema" value="true"></property>
</jdbcConnection>

方法2

mysql的connectionURL中添加 useInformationSchema=true.大致上就是:

connectionURL="jdbc:mysql://127.0.0.1:3306/test?characterEncoding=UTF-8&useInformationSchema=true"

兩種方法任選其一.

詳解

MBG訪問數據庫也是經過JDBC進行,而經過JDBC鏈接Oracle、Mysql(其它數據庫暫不清楚)時,想獲取到表及字段註釋是須要額外設置一些鏈接屬性的.通常大致上都是以下的代碼(以Oracle爲例):

Properties props =newProperties();
props.put("remarksReporting","true");//Oracle
dbConn = DriverManager.getConnection(url, props);
DatabaseMetaData dbmd = dbConn.getMetaData();

這樣經過JDBC就能獲取到表或者字段的註釋了.

那麼在MBG中怎麼設置呢?總不能去改源碼吧.其實MBG自身已經提供瞭解決方法.

咱們先來看下MBG鏈接數據庫的代碼,能夠在org.mybatis.generator.internal.JDBCConnectionFactory中找到:

//如下代碼來自Mybatis Generator 1.3.5
/**
 * This constructor is called when there is a JDBCConnectionConfiguration
 * specified in the configuration.
 * 
 * @param config
 */
public JDBCConnectionFactory(JDBCConnectionConfiguration config) {
    super();
    userId = config.getUserId();
    password = config.getPassword();
    connectionURL = config.getConnectionURL();
    driverClass = config.getDriverClass();
    otherProperties = config.getProperties();//注意此行
}

public Connection getConnection()
        throws SQLException {
    Driver driver = getDriver();

    Properties props = new Properties();

    if (stringHasValue(userId)) {
        props.setProperty("user", userId); //$NON-NLS-1$
    }

    if (stringHasValue(password)) {
        props.setProperty("password", password); //$NON-NLS-1$
    }

    props.putAll(otherProperties);//注意此行

    Connection conn = driver.connect(connectionURL, props);

    if (conn == null) {
        throw new SQLException(getString("RuntimeError.7")); //$NON-NLS-1$
    }

    return conn;
}

經過上面代碼(尤爲是我加了注意此行註釋的兩行代碼)咱們能夠看到,MBG在創建鏈接時,是把JDBCConnectionConfiguration中的全部properties給設置進去了.那麼顯然咱們只須要找到在哪配置這些properties就好了.

JDBCConnectionConfiguration對應到XML配置裏就是jdbcConnection節點.

再來看看官方的使用文檔,官方文檔關於jdbcConnection (點擊查看) 一節中 <property>子元素的說明:

<property> (0..N) Note: any properties specified here will be added to the properties of the JDBC driver.

那麼在配置文件中咱們以下改動便可:

<jdbcConnection driverClass="${driver}"
    connectionURL="{url}" userId="${username}" password="${password}">
    <!-- 針對oracle數據庫 -->
    <property name="remarksReporting" value="true"></property>
</jdbcConnection>

其它相關

• 關於如何生成自定義註釋,參見 mybatis-generator自定義註釋生成

 

原始實例

1 目錄

2 generate.bat

java -jar mybatis-generator-core-1.3.7.jar -configfile generator_oracle.xml -overwrite

 

3 generator_oracle.xml

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN" "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd" >
<generatorConfiguration>
    <!-- 在項目中會自動找到 -->
	<classPathEntry location="ojdbc14-10.2.0.4.0.jar" />
	<!--
	<properties resource="D:\\workspace-demo\\mybatis-generator-core\\bin\\config_oracle.properties" />
	-->
	<context id="context1">
		<!--oracle.jdbc.driver.OracleDriver or com.mysql.jdbc.Driver  -->
		<jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver" connectionURL="jdbc:oracle:thin:@192.168.5.11:1521:ORCL" 
		userId="USER"   password="PASS">  
    </jdbcConnection>  
		<!-- model -->
		<javaModelGenerator targetPackage="com.spinach.business.test.entity" targetProject=".">
			<property name="enableSubPackages" value="true" />
			<property name="trimStrings" value="true" />
		</javaModelGenerator>
  
  		<!-- mapper -->
		<sqlMapGenerator targetPackage="com.spinach.business.test.dao" targetProject=".">
			<property name="enableSubPackages" value="true" />
			<property name="methodNameCalculator" value="extended" />
		</sqlMapGenerator>  

  		<!-- dao -->
		<javaClientGenerator type="XMLMAPPER" targetPackage="com.spinach.business.test.dao" targetProject=".">
			<property name="enableSubPackages" value="true" />
		</javaClientGenerator>
		
		<!--  schema="dbname" 網絡上說：schema是數據名，加了反而不能生成。 -->
		<table tableName="t_blxx_tbl" enableCountByExample="false"  enableUpdateByExample="false"  enableUpdateByPrimaryKey="false"
           enableDeleteByExample="false" enableDeleteByPrimaryKey="false" enableSelectByPrimaryKey="false" enableSelectByExample="false" selectByExampleQueryId="false" 
           enableInsert="true" 
           >
          <property name="rootClass" value="com.spinach.support.spring.mybatis.entity.MybatisEntity" />
    </table>
		
	</context>
</generatorConfiguration>