MyBatis: 查询分页之拦截器

待我称王封你为后i 2023-07-13 15:29 41阅读 0赞

1.利用Interceptor:

package interceptor;
    
    
    import java.sql.Connection;
    import java.util.Map;
    import java.util.Properties;
    import org.apache.ibatis.executor.parameter.ParameterHandler;
    import org.apache.ibatis.executor.statement.StatementHandler;
    import org.apache.ibatis.mapping.MappedStatement;
    import org.apache.ibatis.plugin.Interceptor;
    import org.apache.ibatis.plugin.Intercepts;
    import org.apache.ibatis.plugin.Invocation;
    import org.apache.ibatis.plugin.Plugin;
    import org.apache.ibatis.plugin.Signature;
    import org.apache.ibatis.reflection.MetaObject;
    import org.apache.ibatis.reflection.SystemMetaObject;
    @Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class,Integer.class})})
    public class MyPageInterceptor implements Interceptor {
    	
    	private int page;
    	private int size;
    	@SuppressWarnings("unused")
    	private String dbType;
     
    	@SuppressWarnings("unchecked")
    	@Override
    	public Object intercept(Invocation invocation) throws Throwable {
    		System.out.println("page plugin invoked...");
    		StatementHandler statementHandler = (StatementHandler)invocation.getTarget();
    		MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
    		while(metaObject.hasGetter("h")){
    			Object object = metaObject.getValue("h");
    			metaObject = SystemMetaObject.forObject(object);
    		}
    		while(metaObject.hasGetter("target")){
    			Object object = metaObject.getValue("target");
    			metaObject = SystemMetaObject.forObject(object);
    		}
    		MappedStatement mappedStatement = (MappedStatement)metaObject.getValue("delegate.mappedStatement");
    		String mapId = mappedStatement.getId();
    		if(mapId.matches(".+ByPager$")){
    			ParameterHandler parameterHandler = (ParameterHandler)metaObject.getValue("delegate.parameterHandler");
    			Map<String, Object> params = (Map<String, Object>)parameterHandler.getParameterObject();
    			page = (int)params.get("page");
    			size = (int)params.get("size");
    			String sql = (String) metaObject.getValue("delegate.boundSql.sql");
    			sql += " limit "+(page-1)*size +","+size;
    			metaObject.setValue("delegate.boundSql.sql", sql);
    		}
    		return invocation.proceed();
    	}
     
    	@Override
    	public Object plugin(Object target) {
    		return Plugin.wrap(target, this);
    	}
     
    	@Override
    	public void setProperties(Properties properties) {
    		String limit = "10";
    		this.page = Integer.parseInt(limit);
    		this.dbType = properties.getProperty("dbType", "mysql");
    	}
     
    }
    
    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
      PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
      "http://mybatis.org/dtd/mybatis-3-config.dtd">
      
    <configuration>
     
    	<properties resource="db.properties"/>
    	
    	<settings>
    		<setting name="logImpl" value="LOG4J"/>
    	</settings>
    	
    	<plugins>
            <plugin interceptor="interceptor.MyPageInterceptor">
               <property name="limit" value="10"/>
                <property name="dbType" value="mysql"/> 
            </plugin>
        </plugins>
    	
    	<environments default="mysql">
    	
        <environment id="mysql">
       
        
          <transactionManager type="JDBC"/>
          
          <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
          </dataSource>
        </environment>
      </environments>
      
      <mappers>
      	<mapper class="org.fkit.mapper.PersonMapper"/> 
      	<mapper class="org.fkit.mapper.CardMapper"/> 
      	<mapper class="org.fkit.mapper.UserMapper"/>
      </mappers>
    </configuration>