第一步:在mybatis配置文件中配置攔截器
<plugins>
<plugin interceptor="x.x.x.x.x.x.xxxInterceptor" />
</plugins>
第二步:實現攔截器
package com.mg.background.common.persistence.interceptor;
import java.util.Properties;
import org.apache.commons.lang3.StringUtils;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlSource;
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.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import com.mg.background.common.persistence.Pages;
import com.mg.background.common.persistence.utils.Reflections;
//攔截器註解,攔截器必須實現Interceptor接口
//AbstractInterceptor實現了Interceptor接口
//@Intercepts的參數中爲@Signature的數組,表示要攔截的類和類中要攔截的方法
//args爲這個方法需要的參數
//MappedStatement.class 爲一個節點對象 即<select/><insert/>之類
//RowBounds.class分頁對象 他的offset和limit屬性表示要展示數據的範圍
//ResultHandler.class結果集映射
@Intercepts({ @Signature(type = Executor.class, method = "query", args = { MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class }) })
public class PaginationInterceptor extends AbstractInterceptor {
private static final long serialVersionUID = 4989671349466153547L;
@Override
public Object intercept(Invocation invocation) throws Throwable {
final MappedStatement mappedStatement = (MappedStatement) invocation.getArgs()[0];
Object parameter = invocation.getArgs()[1];
//boundSql爲一條sql語句動態運行對象
//mappedStatement.getBoundSql(parameter);動態計算sql運行的條件
//即<if/>條件的計算,然後生成要運行的sql
BoundSql boundSql = mappedStatement.getBoundSql(parameter);
//得到入參類型
Object parameterObject = boundSql.getParameterObject();
//獲取分頁參數對象
Pages<Object> pages = null;
if (parameterObject != null) {
//利用反射機制訪問對象屬性
pages = convertParameter(parameterObject, pages);
}
//如果設置了分頁對象,則進行分頁
if (pages != null && pages.getPageSize() != -1) {
if (StringUtils.isBlank(boundSql.getSql())) {
return null;
}
String originalSql = boundSql.getSql().trim();
//得到總記錄數
pages.setTotal(SQLHelper.getCount(originalSql, null, mappedStatement, parameterObject, boundSql, log));
//分頁查詢 本地化對象 修改數據庫注意修改實現
String pageSql = SQLHelper.generatePageSql(originalSql, pages, DIALECT);
// if (log.isDebugEnabled()) {
// log.debug("PAGE SQL:" + StringUtils.replace(pageSql, "\n", ""));
// }
invocation.getArgs()[2] = new RowBounds(RowBounds.NO_ROW_OFFSET, RowBounds.NO_ROW_LIMIT);
BoundSql newBoundSql = new BoundSql(mappedStatement.getConfiguration(), pageSql, boundSql.getParameterMappings(), boundSql.getParameterObject());
//解決MyBatis 分頁foreach 參數失效 start
if (Reflections.getFieldValue(boundSql, "metaParameters") != null) {
MetaObject mo = (MetaObject) Reflections.getFieldValue(boundSql, "metaParameters");
Reflections.setFieldValue(newBoundSql, "metaParameters", mo);
}
//解決MyBatis 分頁foreach 參數失效 end
MappedStatement newMs = copyFromMappedStatement(mappedStatement, new BoundSqlSqlSource(newBoundSql));
invocation.getArgs()[0] = newMs;
}
// }
return invocation.proceed();
}
//綁定插件
@Override
public Object plugin(Object target) {
//如果target有接口返回代理類,沒有返回類本身
//如果代理類wrap方法會綁定一個攔截器,調用plugin的invoke方法
//將攔截的方法的參數初始化成一個Invocation對象 然後調用intercept方法
return Plugin.wrap(target, this);
}
//初始化攔截器時將配置文件中攔截器下配置的properties設置進來
@Override
public void setProperties(Properties properties) {
super.initProperties(properties);
}
private MappedStatement copyFromMappedStatement(MappedStatement ms, SqlSource newSqlSource) {
MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(), newSqlSource, ms.getSqlCommandType());
builder.resource(ms.getResource());
builder.fetchSize(ms.getFetchSize());
builder.statementType(ms.getStatementType());
builder.keyGenerator(ms.getKeyGenerator());
if (ms.getKeyProperties() != null) {
for (String keyProperty : ms.getKeyProperties()) {
builder.keyProperty(keyProperty);
}
}
builder.timeout(ms.getTimeout());
builder.parameterMap(ms.getParameterMap());
builder.resultMaps(ms.getResultMaps());
builder.cache(ms.getCache());
return builder.build();
}
public static class BoundSqlSqlSource implements SqlSource {
BoundSql boundSql;
public BoundSqlSqlSource(BoundSql boundSql) {
this.boundSql = boundSql;
}
public BoundSql getBoundSql(Object parameterObject) {
return boundSql;
}
}
}