Mybatis分页-利用Mybatis Generator插件生成基于数据库方言的分页语句，统计记录总数

 

众所周知，Mybatis本身没有提供基于数据库方言的分页功能，而是基于JDBC的游标分页，很容易出现性能问题。网上有很多分页的解决方案，不外乎是基于Mybatis本机的插件机制，通过拦截Sql做分页。但是在像Oracle这样的数据库上，拦截器生成的Sql语句没有变量绑定，而且每次语句的都要去拦截，感觉有点浪费性能。

Mybatis Generator是Mybatis的代码生成工具，可以生成大部分的查询语句。

本文提供的分页解决方案是新增Mybatis Generator插件，在用Mybatis Generator生成Mybatis代码时，直接生成基于数据库方言的Sql语句，解决Oralce等数据库的变量绑定，且无需使用Mybatis拦截器去拦截语句判断分页。

一、编写Mybatis Generator Dialect插件

/**

 * Copyright (C) 2011 Tgwoo Inc.
 * http://www.tgwoo.com/
 */
package com.tgwoo.core.dao.plugin;

import java.util.List;

import org.mybatis.generator.api.CommentGenerator;
import org.mybatis.generator.api.IntrospectedTable;
import org.mybatis.generator.api.PluginAdapter;
import org.mybatis.generator.api.dom.java.Field;
import org.mybatis.generator.api.dom.java.FullyQualifiedJavaType;
import org.mybatis.generator.api.dom.java.JavaVisibility;
import org.mybatis.generator.api.dom.java.Method;
import org.mybatis.generator.api.dom.java.Parameter;
import org.mybatis.generator.api.dom.java.TopLevelClass;
import org.mybatis.generator.api.dom.xml.Attribute;
import org.mybatis.generator.api.dom.xml.Document;
import org.mybatis.generator.api.dom.xml.TextElement;
import org.mybatis.generator.api.dom.xml.XmlElement;

/**
 * @author pan.wei
 * @date 2011-11-30 下午08:36:11
 */
public class OraclePaginationPlugin extends PluginAdapter {

	@Override
	public boolean modelExampleClassGenerated(TopLevelClass topLevelClass,
			IntrospectedTable introspectedTable) {
		// add field, getter, setter for limit clause
		addPage(topLevelClass, introspectedTable, "page");
		return super.modelExampleClassGenerated(topLevelClass,
				introspectedTable);
	}

	@Override
	public boolean sqlMapDocumentGenerated(Document document,
			IntrospectedTable introspectedTable) {
		XmlElement parentElement = document.getRootElement();

		// 产生分页语句前半部分
		XmlElement paginationPrefixElement = new XmlElement("sql");
		paginationPrefixElement.addAttribute(new Attribute("id",
				"OracleDialectPrefix"));
		XmlElement pageStart = new XmlElement("if");
		pageStart.addAttribute(new Attribute("test", "page != null"));
		pageStart.addElement(new TextElement(
				"select * from ( select row_.*, rownum rownum_ from ( "));
		paginationPrefixElement.addElement(pageStart);
		parentElement.addElement(paginationPrefixElement);

		// 产生分页语句后半部分
		XmlElement paginationSuffixElement = new XmlElement("sql");
		paginationSuffixElement.addAttribute(new Attribute("id",
				"OracleDialectSuffix"));
		XmlElement pageEnd = new XmlElement("if");
		pageEnd.addAttribute(new Attribute("test", "page != null"));
		pageEnd.addElement(new TextElement(
				"<![CDATA[ ) row_ ) where rownum_ > #{page.begin} and rownum_ <= #{page.end} ]]>"));
		paginationSuffixElement.addElement(pageEnd);
		parentElement.addElement(paginationSuffixElement);

		return super.sqlMapDocumentGenerated(document, introspectedTable);
	}

	@Override
	public boolean sqlMapSelectByExampleWithoutBLOBsElementGenerated(
			XmlElement element, IntrospectedTable introspectedTable) {

		XmlElement pageStart = new XmlElement("include"); //$NON-NLS-1$   
		pageStart.addAttribute(new Attribute("refid", "OracleDialectPrefix"));
		element.getElements().add(0, pageStart);

		XmlElement isNotNullElement = new XmlElement("include"); //$NON-NLS-1$   
		isNotNullElement.addAttribute(new Attribute("refid",
				"OracleDialectSuffix"));
		element.getElements().add(isNotNullElement);

		return super.sqlMapUpdateByExampleWithoutBLOBsElementGenerated(element,
				introspectedTable);
	}

	/**
	 * @param topLevelClass
	 * @param introspectedTable
	 * @param name
	 */
	private void addPage(TopLevelClass topLevelClass,
			IntrospectedTable introspectedTable, String name) {
		topLevelClass.addImportedType(new FullyQualifiedJavaType(
				"com.tgwoo.core.dao.pojo.Page"));
		CommentGenerator commentGenerator = context.getCommentGenerator();
		Field field = new Field();
		field.setVisibility(JavaVisibility.PROTECTED);
		field.setType(new FullyQualifiedJavaType("com.tgwoo.core.dao.pojo.Page"));
		field.setName(name);
		commentGenerator.addFieldComment(field, introspectedTable);
		topLevelClass.addField(field);
		char c = name.charAt(0);
		String camel = Character.toUpperCase(c) + name.substring(1);
		Method method = new Method();
		method.setVisibility(JavaVisibility.PUBLIC);
		method.setName("set" + camel);
		method.addParameter(new Parameter(new FullyQualifiedJavaType(
				"com.tgwoo.core.dao.pojo.Page"), name));
		method.addBodyLine("this." + name + "=" + name + ";");
		commentGenerator.addGeneralMethodComment(method, introspectedTable);
		topLevelClass.addMethod(method);
		method = new Method();
		method.setVisibility(JavaVisibility.PUBLIC);
		method.setReturnType(new FullyQualifiedJavaType(
				"com.tgwoo.core.dao.pojo.Page"));
		method.setName("get" + camel);
		method.addBodyLine("return " + name + ";");
		commentGenerator.addGeneralMethodComment(method, introspectedTable);
		topLevelClass.addMethod(method);
	}

	/**
	 * This plugin is always valid - no properties are required
	 */
	public boolean validate(List<String> warnings) {
		return true;
	}
}

 

二、增加插件到Mybatis Generator配置文件中

<?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 >
	<classPathEntry location="E:\work\eclipseWorkspace\myEclipse\CTSPMTS\WebRoot\WEB-INF\lib\ojdbc14.jar" />
	
	<context id="oracle" >
		<plugin type="org.mybatis.generator.plugins.CaseInsensitiveLikePlugin"></plugin>
	 	<plugin type="org.mybatis.generator.plugins.SerializablePlugin"></plugin>
	 	<!-- Pagination -->
	 	<plugin type="com.tgwoo.core.dao.plugin.OraclePaginationPlugin"></plugin>
	 	
	  	<commentGenerator>  
		   <property name="suppressDate" value="true" />  
		    <property name="suppressAllComments" value="true" />
	    </commentGenerator>  
	  	
	    <jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver" connectionURL="jdbc:oracle:thin:@192.168.0.2:1521:ctspmt" userId="ctspmt" password="ctspmt123" />
	    <javaModelGenerator targetPackage="com.tgwoo.ctspmt.model" targetProject="CTSPMTS/src" />
	    <sqlMapGenerator targetPackage="com.tgwoo.ctspmt.data" targetProject="CTSPMTS/src" />
	    <javaClientGenerator targetPackage="com.tgwoo.ctspmt.data" targetProject="CTSPMTS/src" type="XMLMAPPER" /><!--
	  
	    <table schema="ctspmt" tableName="mt_e_interface_log"/>
	    --><!--
	    <table schema="ctspmt" tableName="mt_e_msg" />
	    <table schema="ctspmt" tableName="mt_e_msg_log" />
	    <table schema="ctspmt" tableName="mt_e_msg_receiver" />
	    <table schema="ctspmt" tableName="st_e_org" />
	    <table schema="ctspmt" tableName="st_e_role" />
	    <table schema="ctspmt" tableName="st_e_user" />
	    <table schema="ctspmt" tableName="mt_e_user_msg_conf" />
	    <table schema="ctspmt" tableName="mt_j_user_device" />
	    <table schema="ctspmt" tableName="st_j_user_role" />
	    <table schema="ctspmt" tableName="ST_E_UNIQUE_KEY" />	 	
	 	--><table schema="ctspmt" tableName="mt_v_msg_item" />
	 </context>
	 
</generatorConfiguration>

 

三、示例

/**

 * Copyright (C) 2011 Tgwoo Inc.
 * http://www.tgwoo.com/
 */
package com.tgwoo.ctspmt.test;

import com.tgwoo.core.config.SpringBeanProxy;
import com.tgwoo.core.dao.pojo.Page;
import com.tgwoo.ctspmt.data.MtVMsgItemMapper;
import com.tgwoo.ctspmt.model.MtVMsgItemExample;

/**
 * @author pan.wei
 * @date 2011-11-25 下午01:26:17
 */
public class Test {
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		//get spring mapper instance 
		MtVMsgItemMapper mapper = SpringBeanProxy.getCtx().getBean(
				MtVMsgItemMapper.class);
		MtVMsgItemExample ex = new MtVMsgItemExample();
		Page page = new Page(0, 10);
		ex.setPage(page);
		ex.createCriteria().andMsgCodeEqualTo("222");
		// set count,up to you
		page.setCount(mapper.countByExample(ex));
		int row = mapper.selectByExample(ex).size();
		System.out.println("============row:" + row + "================");
	}

}

 

四、分页类

 

package com.tgwoo.core.dao.pojo;

/**
 * @author pan.wei
 * @date 2011-12-1 上午11:36:12
 */
public class Page {
	// 分页查询开始记录位置
	private int begin;
	// 分页查看下结束位置
	private int end;
	// 每页显示记录数
	private int length;
	// 查询结果总记录数
	private int count;
	// 当前页码
	private int current;
	// 总共页数
	private int total;

	public Page() {
	}

	/**
	 * 构造函数
	 * 
	 * @param begin
	 * @param length
	 */
	public Page(int begin, int length) {
		this.begin = begin;
		this.length = length;
		this.end = this.begin + this.length;
		this.current = (int) Math.floor((this.begin * 1.0d) / this.length) + 1;
	}

	/**
	 * @param begin
	 * @param length
	 * @param count
	 */
	public Page(int begin, int length, int count) {
		this(begin, length);
		this.count = count;
	}

	/**
	 * @return the begin
	 */
	public int getBegin() {
		return begin;
	}

	/**
	 * @return the end
	 */
	public int getEnd() {
		return end;
	}

	/**
	 * @param end
	 *            the end to set
	 */
	public void setEnd(int end) {
		this.end = end;
	}

	/**
	 * @param begin
	 *            the begin to set
	 */
	public void setBegin(int begin) {
		this.begin = begin;
		if (this.length != 0) {
			this.current = (int) Math.floor((this.begin * 1.0d) / this.length) + 1;
		}
	}

	/**
	 * @return the length
	 */
	public int getLength() {
		return length;
	}

	/**
	 * @param length
	 *            the length to set
	 */
	public void setLength(int length) {
		this.length = length;
		if (this.begin != 0) {
			this.current = (int) Math.floor((this.begin * 1.0d) / this.length) + 1;
		}
	}

	/**
	 * @return the count
	 */
	public int getCount() {
		return count;
	}

	/**
	 * @param count
	 *            the count to set
	 */
	public void setCount(int count) {
		this.count = count;
		this.total = (int) Math.floor((this.count * 1.0d) / this.length);
		if (this.count % this.length != 0) {
			this.total++;
		}
	}

	/**
	 * @return the current
	 */
	public int getCurrent() {
		return current;
	}

	/**
	 * @param current
	 *            the current to set
	 */
	public void setCurrent(int current) {
		this.current = current;
	}

	/**
	 * @return the total
	 */
	public int getTotal() {
		if (total == 0) {
			return 1;
		}
		return total;
	}

	/**
	 * @param total
	 *            the total to set
	 */
	public void setTotal(int total) {
		this.total = total;
	}

}

 五、生成后的代码

1、Example代码

 

 

package com.tgwoo.ctspmt.model;

import com.tgwoo.core.dao.pojo.Page;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

public class MtVMsgItemExample {
    protected String orderByClause;

    protected boolean distinct;

    protected List<Criteria> oredCriteria;

    protected Page page;
   
    ...

 2、mapper.xml

 

...
 <select id="selectByExample" resultMap="BaseResultMap" parameterType="com.tgwoo.ctspmt.model.MtVMsgItemExample" >
    <include refid="OracleDialectPrefix" />
    select
    <if test="distinct" >
      distinct
    </if>
    <include refid="Base_Column_List" />
    from CTSPMT.MT_V_MSG_ITEM
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null" >
      order by ${orderByClause}
    </if>
    <include refid="OracleDialectSuffix" />
  </select>
...
  <sql id="OracleDialectPrefix" >
    <if test="page != null" >
      select * from ( select row_.*, rownum rownum_ from ( 
    </if>
  </sql>
  <sql id="OracleDialectSuffix" >
    <if test="page != null" >
      <![CDATA[ ) row_ ) where rownum_ > #{page.begin} and rownum_ <= #{page.end} ]]>
    </if>
  </sql>
...

 

 

附件是Mybatis Generatorjar包。

其他数据库的方言可以按照Oracle的去改写，有写好的希望能共享下。

 

 

-------------------------------------------------------------------------------------------------------

maven管理：

1、pom.xml

<build>
		<plugins>
			<plugin>
				<groupId>org.mybatis.generator</groupId>
				<artifactId>mybatis-generator-maven-plugin</artifactId>
				<version>1.3.1</version>
				<executions>
					<execution>
						<id>Generate MyBatis Artifacts</id>
						<goals>
							<goal>generate</goal>
						</goals>
					</execution>
				</executions>
				<dependencies>
					<dependency>
						<groupId>com.oracle</groupId>
						<artifactId>ojdbc14</artifactId>
						<version>10.2.0.4.0</version>
					</dependency>
				</dependencies>
			</plugin>
		</plugins>
	</build>

 

 

 

 2、generatorConfig.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>
	<context id="oracleGenerator" targetRuntime="MyBatis3">
		<plugin type="org.mybatis.generator.plugins.CaseInsensitiveLikePlugin"></plugin>
		<plugin type="org.mybatis.generator.plugins.SerializablePlugin"></plugin>
		<!-- Pagination -->
		<plugin
			type="com.tgwoo.test.core.dao.mybatis.generator.plugin.pagination.OraclePaginationPlugin"></plugin>

		<!-- 取消注释 -->
		<commentGenerator>
			<property name="suppressDate" value="true" />
			<property name="suppressAllComments" value="true" />
		</commentGenerator>
		<!-- 配置连接数据信息 -->
		<jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver"
			connectionURL="jdbc:oracle:thin:@192.168.0.2:1521:test" userId="test"
			password="test123" />
		<javaTypeResolver>
			<property name="forceBigDecimals" value="false" />
		</javaTypeResolver>

		<!-- 配置自动生成的Model的保存路径与其它参数 -->
		<javaModelGenerator targetPackage="com.tgwoo.test.dao.model"
			targetProject=".\src\main\java">
			<property name="enableSubPackages" value="false" />
			<property name="trimStrings" value="true" />
		</javaModelGenerator>

		<!-- 配置自动生成的Mappper.xml映射的保存路径与其它参数 -->
		<sqlMapGenerator targetPackage="com.tgwoo.test.dao"
			targetProject=".\src\main\resources">
			<property name="enableSubPackages" value="false" />
		</sqlMapGenerator>

		<!-- 配置自动生成的Mappper.java接口的保存路径与其它参数 -->
		<javaClientGenerator type="XMLMAPPER"
			targetPackage="com.tgwoo.test.dao" targetProject=".\src\main\java">
			<property name="enableSubPackages" value="false" />
		</javaClientGenerator>

		<!-- 生成表对应的操作与实体对象 -->
		<table schema="test" tableName="testTable">
			<columnOverride column="id" javaType="Long" />
		</table>
	</context>
</generatorConfiguration>

 

 3、run

Goals:mybatis-generator:generate

 

4、注意事项

报插件无法找到或者无法实例化的一般是分页插件和maven插件不在同一classloader下引起的，需要在mybatis-generator-maven-plugin的dependencies中增加dependency。

评论

12 楼 lanbo316 2015-06-30  

[/size][align=left][size=xx-large][/ align]

11 楼 luoyongsir 2013-11-06  

yueai22 写道

唉。。我的报插件无法找到或者无法实例化。。。但是mybatis-generator-maven-plugin的dependencies中也增加dependency。但是还是报这个错。

哦我也是，你是怎么解决的？

10 楼 luoyongsir 2013-11-06  

我用的sql server 数据库，但是报：generate failed: Cannot instantiate object of type com.montnets.luoy.dao.plugins.PaginationPlugin 不知道有没有人解决了同样的问题的。

9 楼 yueai22 2013-01-06  

java.lang.RuntimeException: Cannot instantiate object of type xxxx.utils.OraclePaginationPlugin

8 楼 yueai22 2013-01-06  

唉。。我的报插件无法找到或者无法实例化。。。但是mybatis-generator-maven-plugin的dependencies中也增加dependency。但是还是报这个错。

7 楼 蜀山红日 2012-12-03  

oracle不支持rownum<=?啊

6 楼 duohuoteng 2012-07-06  

cv

5 楼 panqili2120 2012-05-28  

很强大 支持 呵呵，但在我们用的Page一般的begin是从1开始的， 也就是说上面的SQL的这部分也改成row_ ) where rownum_ >= #{page.begin}这样

4 楼 hgdakfg 2012-03-21  

hellostory 写道

如果是做【高级查询】分页显示，你这个如何实现？

写视图.

3 楼 chengfengmuyu 2012-02-19  

2 楼 daquan198163 2012-02-08  

Good，太有用了！

1 楼 hellostory 2012-02-07  

如果是做【高级查询】分页显示，你这个如何实现？